Well, there are a few folks who are on the phone quite a bit, but if you need privacy this is not the best setup. There is a small "phone room" with a desk and a door, but just the one.

However, I believe some of the other co-working spaces in SF (including the other NextSpace ones further into the city) have multiple phone booths so you may want to check those out. Drop-in cost for most spaces tends to be about $20 - $25/day.