What area, so cal can be anywhere? Here is san diego between the bigger shops ide say Ocean Enterprises & House Of Scuba are the largest, both have websites but no pool...
Just read on their fb page that dive california does have an onsite pool & can demo / try equipment. Would imagine they arent going to let you dip a new bc but you can dip a similar rental, large rental selection as they even rent bp&w's...
I cant say that dive california has a huge selection of bc's onsite compared to OE & House of Scuba.
OE also has demo days where they load-up all sorts of equipment & reps on hand with their gear & to answer questions, at a local pool. Once a year I think, you would have to call & ask.
OE carries all the namebrand bc, SP & AL, etc vs House of Scuba has quiet a few middle of the road brands where you can find further savings if thats the route you choose.
If you end-up checking out HOS, they have their store front but lots of gear in the back warehouse which is not on display but will take you back there as they are working with you if needed.
http://www.houseofscuba.com/
http://www.oceanenterprises.com/
http://www.divecalifornia.com/Menu_Dive_Shop/Shop.html
Just curious, what shop did you get your certification through?