I have done dial-up internet access each time I have stayed at Hilton Head. Just make sure that you have a truly "local" number before you leave and that you check out your dial-up modem settings so you know they work before you try from HH. If you have a local number, then the cost is only $0.35 for the call. The lines are not real clean, but I've been able to get in the 28K - 42K range of connection.
I've not found any real broadband connection at HH. The rooms are not wired for ethernet and I have not seen any place to plug into a broadband hub in the common rooms. It sure would be nice if they would put in a cable broadband connection and a router in the Den, so we could do high speed connection. I know I'd pay the $3 / day cost.
One lesson learned - bring a long phone cord, as the phone connection is not near the table where I put my laptop.