I've been living in Zacatecas since September 2008.
There is NO American Community here. Five, count 'em, five fulltime residents.
I chose Zacatecas because it is small enough to get around easily but large enough to have all conveniences including Wal-Mart and Sam's Club. It also has distinct seasons. Gets down to freezing at night in winter, rarely higher than 90 in summer. To me that's a positive, to others a negative. The city is safe and the people are predominantly friendly and honest. Learn your way around, make friends with neighbors and you won't get taken.
There are enough English speaking tourists who come through here that you can do OK with just survival Spanish; much better if you have a fair command of Spanish so you can enjoy the rich Mexican culture for which Zacatecas is noted.
You can rent a nice place for anywhere from $400 a month to $4000 and up. Nice houses to buy start at around $150,000 and the sky's the limit. It all depends on what level of luxury or modernity you require. There's none of the price inflation for gringos found in retiree meccas.
Taxi drivers will try to include a tip (tipping cab drivers is not customary) in the fare. Once you get to know the fare the tactic is to tell the driver just before paying, "That was 20 peso, correct?" Normally, that works. If he asks for 5 pesos more, why fight? That old advice of asking first is almost useless anywhere in Mexico. You may spend ten minutes arguing and end up paying the same as if you didn't ask. Taxi fares are cheap. The most I ever paid was 45 pesos (around $4.00) and that was from one end of the city to the other.
In general, don't expect things to happen on time. It's not a matter of "mañana," it's that people don't want to tell you something that will disappoint. They tell you what they think you want to hear. Hey, you're retired, what's the hurry?
If you have to deal with any Mexican government agency starting with the consulate where you do your initial paperwork, it's best to go in person and not rely on phone calls. You'll probably have to wait in a long line, but you'll be able to get a list of requirements in writing. Read carefully and ask about anything you don't understand. That will avoid missteps and additional return trips to the consulate. It will take 3 to 4 trips to the consulate to get you FM2 or FM3 (the document that lets you reside in Mexico) and the permission to make arrangements to ship you household goods. For the move deal with a major moving that has connections with a company that specializes in international moves. Even with the best of professional help, figure on your goods being in transit for 6 weeks.
Once you get to Mexico you will have to register you FM document with the local office of INAM (Mexican National Migration Institute.) All state capitals have one (Zacatecas is a state capital) and there are offices in smaller towns too but service could be spotty or unreliable. Again, it's best to go in person. It's a multi-step process that will probably require 2 trips to complete the paperwork and one more to pickup the document that has to be sent to Mexico City to be endorsed.
In all this red tape, I did not encounter anyone who tried to make things difficult. Everyone was courteous and tried to be helpful. Bureaucracy is what it is.
I should mention that you can't rely on what you find on the internet, even Mexican government websites. Consulates and INAM have a great deal of autonomy and may be stricter or more lenient depending on who is in charge.
Getting cable and internet installed took three weeks the first place I lived and am going into my third week in the place I just moved to. This time their excuse was that they couldn't find the address. Possible, it's kind of hidden in a quiet corner. They'll get here eventually. My landlord was kind enough to give me access to hi wi-fi so I'm not cut off from the outside world.
I signed up for Skype's $59.99 unlimeted US and Canada Plan which gives me unlimited calls out and a US number friends and family can dial which connects to my computer. International rates are high from a Mexican landline even higher from a cellphone. I've only needed a cell phone here so far. I'm spending lass than $40 a month, mostly texting and a few voice calls. Most of my Mexican friends have Skype so we talk computer to computer.
I have a mail suite in McAllen TX for stuff I buy on the internet and other mail I don't want to trust to the Mexican Post Office.
McAllen is a 10 hour bus ride from Zacatecas, maybe 8 by car. I don't need a car at all in Zacatecas so I don't have one. The busses are clean, comfortable, reliable and have meal stops where the food is good and safe. Over age 60 you can apply for a 50% discount. That makes the roundtrip fare come out to $35-45. I can make my irregular runs without staying overnight or I stay at LaQuinta if I feel like it. I like the bus because it seems quicker to get through customs than by car or plane.
I've rented a car in Mexico several times for sightseeing trips. Rates are very reasonable and include full insurance.
I have a maid that comes in 2 or 3 days a week to do the cleaning, food shopping, cooking and laundry. I guess I pay around $60 a week including the cost of food. If I'm paying a bit more than the going rate, she's a great cook and is worth it.
Zacatecas is a good jumping off spot for travel to other parts of Mexico. Roads south are excellent and there's lot's to see.
All in all, I have been happy and comfortable here for over a year, expect to continue to be so and look forward to further travels and 'adventures' here in Mexico and maybe other parts of latin America.
What is an advantage or disadvantage, you'll have to decide for yourself. Do some looksee trips. Do some reading. Enjoy the search.
My first and only looksee trip was to Zacatecas. It was everything I was looking for and more, fell in love with the place and decided right then and there. Then, I took 4 months getting ready, doing the paperwork and moving.
Take your time and take it easy.