Grounding your mast should not impair your signal at all. One of the regulars on the board, GroundUrMast, knows a great deal about grounding. We've recently had a discussion about both grounding and surge protectors here:
http://forum.tvfool.com/showthread.php?t=10888
Personally, I'll be curious if you can get access to your service ground. SDGE has done a great job of zipping mine up tight.