Costa Rica on a $100 per day or less budget.

Apartments are generally rented by the month...not just for a few days, especially when not in a tourist area.

In an 'upper class area' an apartment it would be much more $60 .... and as for $30, no way...

Best to get a hotel room for such a short period...and even then you will pay more than you budget specifies.

$20... including taxes of 13%... for 2 meals, may not get you some good meals in a nice restaurant but will be enough to eat at  a 'soda' or a fast food outlet.

I disagree with the above YES ot ispossible email me for advice and hlpe K must live in Gringo Gulches.. BUT the areas YOU mention  such as San Jose and Caribbean Coast are VERY dangerous so be careful.  The other Santa Ana is a "Gringo Gulch " so YES they charge more for EVERYTHING
(I HAVE lived there and you do not get the real feel of Costa Rica. ) .unless you want to feel that you are in an overpriced part of Los Angeles:( 
Here  in Heredia and its Hills of Beauty,  as I have mentioned MANY times you can have a delicious meal with juice for $4 or in  upscale restaurant FANTASTIC real thick Steak for $18 or less..with  additional extras at no charge,,, ...IN the Gulches costs double IF you find a tender piece of meat...
So emai; ***
You CAN enjjoy at that price but avoid the danger spots...and he Gulches:)

If you're looking to travel cheap, I'd look elsewhere.  Costa Rica is not cheap unless you don't mind a rural Tico village, and then your amenities might be very limited and English would be very limited.  I would check out AirBnb or VRBO.

If you want a really cheap vacation, look at Nicaragua.

true you get what you pay for and anyone who KNOWS Nica can never compare it to CR., Its like comparing a Cheap 2nd hand car to a newer cleaner  better bmodel yes?

I am spending time in Nicaragua also during this trip. I speak enough Spanish to survive and travel. If no one speaks any English, Eso No es un problema.

I have viewed those websites for places to stay. I would not solely decided which community to stay, without opinions from others. They are trying to make money renting their places.

This is the reason i posted the question on this forum.

Most foreigners do favour residing in gringoland separate from the local population. I do not have an opinion to offer on that choice. It is a personal preference. All advice is appreciated.

My priority is, " I would like access to a frequent and multiple bus route, middle or upper economic class neighbourhood of local people, quite every day of the week and during the night. "

Thanks in advance

Again I say do yourself a favor and check out the HEREDIA Hills areas and find all that you mentioned//Good Luck