Low-cost Caribbean vacation for January

I'm looking for a low-cost Caribbean vacation for 5-6 nights for two
people, each with their own room for under $650 per person including
airfare from Boston for the first week in January 2004. We want to be
within walking distance of a beautiful sandy beach which is swimmable
and preferably with some waves (not still water). Package deals don't
seem to be an option since we each want our own room (my friend is a
heavy snorer) so we're needing to look into airfare and accommodation
separately.

After extensive research, the best option I've found is Isla Mujeres
off Cancun - I think we can come up with airfare for $350 per person
and accommodations near the beach for $50 per person. My guess though
is that we can do better on the airfare if we keep looking.

Anyone have comments/suggestions related to the above option (wasn't
the Cancun area hit with bad hurricane damage the past year - and what
effect has that had? and what low-cost lodging do you most recommend
in Isla Mujeres? We've found a few possibilities already at the I-M
website) or any other suggestions? Much appreciated.

Tracy