Relax - We are not a 3rd world county and everyone on this message board obviously has internet. LOL
Many people here derive their income from internet work. There are three speeds available and cost appropriately.
You are asking about apartment – most rentals here are condos or houses – the main economy here being tourists. I may be wrong but I think most condos now are wired for internet.
You mention $500 (I am guessing you are speaking US dollars). If you find anything for that price I’m fairly sure you would be expected to pay for utilities; internet, electricity (can get expensive) and water ($.10 BZ a gallon) plus bottled water for drinking ($3 or $4 BZ per 5 gallons.)
November may seem like a good time to come but it is the end of the rainy season here and the beginning of high season. So November, December and January will be the most expensive.
Good luck with your search.