Cheapest Place To Live?

Hey guys,

I'm in India right now, but my visa runs out soon. Was thinking of moving to somewhere warm for a few months so I can knuckle down and get some work done (I do internet marketing). So I want to find somewhere cheap to live (US$500 a month or under), hopefully on the beach, with a chilled out vibe, and a good reliable internet connection. I've always wanted to learn Spanish so thought this would be a great opportunity, thats why I'm posting in the Caribbean/West Indies section... I also posted the same thing on the Mexico, South America, and Central America board.

Any ideas?

P.S. I love to scuba dive. It's not a deciding factor, but somewhere with good diving would be a plus too

Thanks!