Great question - my sister got married in Mexico last year at a medium sized resort. The wi-fi was spotty and I certainly didn't want to be carrying my phone around to the pool and beach anyway - I pretty much left it in the safe the whole trip. People generally congregated at the buffet for breakfast and then at the swim-up bar during the day. It ended up being fine. I'm definitely thinking of giving people a bracelet or some marker so people will know they are part of the same group when they run into each other.
I do think it is a great idea to make a list of guests and their room numbers. We thought of this for my sister's wedding, but it proved sort of challenging with people arriving at all different times and days - and the resort didn't assign room numbers until you check in. So some people might have been there for 2-3 days when others were arriving so the list would be changing a lot.
It sounds like the Canadians on here might have an easier time if you have everyone arriving on the same charter! That sounds so awesome, but not feasible for my guests coming from all over the US.