One of my friends got her BS from SPC, I have to say that is an extremely expensive school comparitively. You might want to look at one of the other schools in Florida and check the tuition costs before you choose St. Pete's.
Currently there is no reason to go for a BS before you start working as a veterinary technician. No state in the US requires a BS to work as a credential vet tech so you can start work as soon as you earn your AS and then decide whether the BS is worth it to you. The cost is often not easy to balance with the benefit of the BS unless you are in a very special situation where a BS is preferred. Or unless you simply want it for yourself and the cost of the education is not an issue.
Volunteering at the SPCA can be of use just because you then have more hours of experience working with animals of different temperaments and dealing with the need for cleanliness and maintaining good control over the animals. But if you can, volunteer at a veterinary clinic instead or at the very least go ahead and shadow a veterinary technician for several days before you decide to embark on your degree in veterinary technology. The work is often not what people expect.