The Tropical Star is pretty cheap (about $15-16US a nite for 2 peeps) It's right on the Front Page.

For the same rate, towards the south end and about a 1/4 mile from the Front, are Orlada and Martha's cabanas. There's a pier right on the beach you can swim from and Martha will do your laundry for about $10BZ a pop. They're also the coolest people.