Hola beatcop49,
Considering your wife's experience, I would suggest trying to find contract or other work she can do REMOTELY from Costa Rica. Many, many companies are moving into 100% remote work schedules. I work for a large multinational in Costa Rica. My company has people working 100% remotely in the States often. But you could easily do something like that from a Costa Rica location with the right set up. You would need to set up automated deposits for salary and you could apply for residency in Costa Rica based on that income.
Technology infrastructure in Costa Rica can be a challenge if you live in a remote area or somewhere with older infrastructure. When looking for housing (which I would recommend you do with a qualified Costa Rica real estate agent), make sure your agent understands you need top of the line technology infrastructure. Skype works great for calls to the States or anywhere else in the world. You can get 3MB internet connect for around $100 US per month depending on what kind of deal you make when you sign up. A good used laptop can be picked up here for around $800 US or so depending on what you need or buy one in the States right before you move down.
The key here is your wife won't find work remotely as a nurse, but she could more than likely find employment as a consultant or contractor using her nursing knowledge in many fields for US insurance companies or pharma companies. You never know. Check Monster, Yahoo, LinkedIn and other avenues to look for remote contract consulting gigs at first (start now in the States). Then as she finds out what is in the market, go for a more perm gig.
Costa Rica, like most countries, has its own immigration challenges. As a result, getting a work permit here is difficult (as mentioned in a previous post). I have a work permit only because I work for a large multi national who sponsored my move and has invested several million dollars in Costa Rica. Getting a work permit in Costa Rica is similiar in difficulty to getting an H1-B in the US; which is not easy to get right now.
So I'd suggest going with the remote work approach. I think you'll have more luck.
Also check out therealcostarica.com website. Tim's site is an excellent source for info on all things Costa Rica for your situation. Tim specializes in retirement here. My husband took his tour before we moved down and learned a lot. Do make sure you learn some Spanish. You don't need to be fluent. But knowning enough to get directions, mail a letter, go to the grocery store and navigate in general is extremely effective. you can function here in English only mode. But you'll pay more for everything, get lost a lot, be treated like a tourist every where you go (not always the best) and get frustrated a lot.
My apologies for the long post. But I've lived here only 7 months and continue to learn more every day here. Costa Rica is an incredible country. It's probably the best country in Central America. The government is stable. Security is pretty much like any US city. The air and water are WAY cleaner. Healthcare is exceptional and a tenth of the price in the US even for top of the line private care. However, cars, electronics and anything imported from the US are twice the price you're paying now in the US. Roads are horrible (which means traffic is horrible). Americans are all assumed to be very rich (translation: your price will always start at twice or more what a Tico would be offered). There is no Target and the mail service is not reliable (you'll need to use a mailing service like Aerocasillas).
Do your homework and you'll do fine. Just remember, there are people coming to Costa Rica everyday from the US and people returning to the US every day from Costa Rica. If you expect to live like you do in the States, you will be on the "returning end" very soon. If you can adapt and live more like a Tico (native Costa Rican) you'll love it here. I've learned to forgo my beloved Missouri Freestone peaches and instead learn to love mangos the size of softballs and pineapple picked literally that morning. In Costa Rica, the concept of "time and space" is very important. It means, your time and your space don't matter.
Ticos take life as it comes. That means they take traffic, long lines, rude foreigners, high prices, low wages, whatever with a grace I've not seen in many cultures. But for Americans it means learning to live at a slower pace where waiting in line is a spectator sport.
I wish you the best of luck. It's an awesome country. Just be prepared with an umbrella, a good pair of walking shoes, a great pocket Spanish dictonary and a very large supply of patience and perserverance. 
Pura Vida!