The good news about the PGRE, is that it is possible to well on it just by studying the right things. A good score is probably more of a reflection on how much someone studied for the test, then really how much physics they know or how well they'll do in grad school. The fact that you have a math degree should help, but being out of school for 10 years means that everything is probably pretty rusty. I think math is definitely a skill that must be practiced, but I'm sure you know that. Also, not having a physics undergrad degree is going to be a distinct disadvantage, you'll have some catching up to do. But for a determined and intelligent person, I think it is entirely possible.
When do you plan on taking the test?
If you only buy one text, I would recommend Halliday, Resnick, and Walker (isbn=978-0471216438) Fundamentals of Physics
. You'll find more recommendations for this text in this site also. Of course, the most valuable resource is the 4 practice PGRE tests, available in various places, more info elsewhere in this site. Another option is the REA "Purple Text" which I studied from. Good for some more practice problems, but hardly representative of what you'll find on the real PGRE. I interspersed my practice tests with my studying, using the problems that I missed or didn't know to direct my studying. I always took them under test like conditions (timed, etc...) to help get a feel for pace and encourage me to improve my speed. A good source for reviewing the answers to the practice tests is: GREPhysics
. Do lots and lots of practice problems, make flash cards, and go over the answers until you actually understand the material, it'll help.