I have surfed Rincon and surrounding areas for years without reef booties. There are breaks that aren't to bad as far as the reef and sea irchins are concerned; however, there are areas that are bad, and you only have to step on one irchin to ruin your trip. I'd bring a pair.
Ive been down there 4 times now, and have never brought reef booties. However keep in mind i always leave with a couple good scrapes and cuts on my feet/anywhere else you might smack into the reef. The reefs are all pretty much dead in this area, so you arn't going to step on any live coral or anything, but if your accustomed to surfing on sand on the east coast, a good reef can be a shocking change.
Just don't put your feet down to push off the bottom and you should be fine. And when you wipe out, try to avoid going too deep. I once saw a guy with a pincushion back after a bad wipe out at Doņa Maria's. Urchin spines are especially brittle and VERY difficult to remove effectively, so to repeat, don't put your feet down to touch bottom, booties or no booties.