If that is Sand Castle formerly Sandpiper at La Siesta that looks tough to beat, although RP gives you a lot in walking distance which may be a nice change after Belair. We enjoy trying new places.

Cell phone is a personal financial choice based on how much it means to you. Yes you can go wifi and do wifi calling and such or you can pay to have data and use where ever which is what we do. So I spend a bit, oh well as it is still minimal, but check with your cell provider on options. I am on Verizon, and note that having access to phone and data during our stay noting we both work still allows us to be there for three or so weeks.
Cheers,
T