I've been in Playa for the last month so I can give you some intel on prices. I'm not a diver so don't know much about that other then everyone says Cozumel is awesome as are some of the cenotos. I haven't been to Merida, but a buddy of mine goes fairly often and says its a cool place to set up shop, but not really a destination spot.
Price wise things definitely start to creep up as you get closer to mid November. However, you may still be able to get some low season pricing on rentals, especially off of 5th ave. A lot of people will discount you up until about mid November. What I did was mass email any host on Airbnb who's nightly rate was under $70 a night and told them I had a monthly budget of $500/$600. I got a lot of rejections, but in the end I had about 8 apartments to choose from in that price range even though there advertised prices where much high for a month. This approach will probably work for you if you have the time to do it.
Foodwise, prices are cheap as long as you stay off of 5th avenue. there are a ton of restaurants and taco stands on 30th avenue, where you can get a full meal for between $50 and $100 pesos. two of my favorites are the taco stand in front of Mega on 30th ave and Papacharly's on 30th street between 25th and 30th ave. Also checkout the website. http://www.everythingplayadelcarmen.com they have a list of restaurants that have lunch/dinner specials under $100 pesos.
Price wise things definitely start to creep up as you get closer to mid November. However, you may still be able to get some low season pricing on rentals, especially off of 5th ave. A lot of people will discount you up until about mid November. What I did was mass email any host on Airbnb who's nightly rate was under $70 a night and told them I had a monthly budget of $500/$600. I got a lot of rejections, but in the end I had about 8 apartments to choose from in that price range even though there advertised prices where much high for a month. This approach will probably work for you if you have the time to do it.
Foodwise, prices are cheap as long as you stay off of 5th avenue. there are a ton of restaurants and taco stands on 30th avenue, where you can get a full meal for between $50 and $100 pesos. two of my favorites are the taco stand in front of Mega on 30th ave and Papacharly's on 30th street between 25th and 30th ave. Also checkout the website. http://www.everythingplayadelcarmen.com they have a list of restaurants that have lunch/dinner specials under $100 pesos.