I used to live in the area, but I can't afford it anymore and now I'm in Dallas, TX.
Both San Ramon and Pleasanton are really nice, you can't go wrong renting from either one. The rent price obviously varies depending upon the size of the home, the updates etc. The commute also varies depending upon what time you need to get to work and from what point in Pleasanton to what point in San Ramon. If you are concern about the commute then I would suggest that you rent a place closest to work.
I highly suggest that you work with a local realtor to assist you in finding what you are looking for.
Susie Kay, Realtor
Certified Home Stager & Senior Real Estate Specialist
United Real Estate Dallas