Unfortunately, yes, the Paulownia tomentosa (Princess Tree) will grow in San Marcos. I'm sure you can find them for sale very easily, but we aren't going to help you with that. If you plant one, we predict that in two years you will be writing to ask us how to get rid of it-or your neighbors will. This plant originated from China, and has been in the United States since about the 1840's. It gets into disturbed areas, like recent burn areas or construction areas, can't be killed and begins to proliferate itself with abandon. It moves into established native forests and begins to crowd out the desirable trees. There are groups, including the Lady Bird Johnson Wildflower Center, who are tracking and reporting this very undesirable plant. Please read this article from the Plant Conservation Alliance's Alien Plant Working Group LEAST WANTED.
What else can we say to discourage you from planting this tree? Please don't.