Of course, check with your doctor to get his/her opinion!! That's worth much more than mine!
However, my personal experience: I was GBS positive during both my pregnancies, and received the antibiotics during labor and had no problem. It's fairly common.
I was very fearful last year for my second delivery, as I had such a difficult recovery after my first daughter was born (pushing 2 hours, 43 minutes, vacuum delivery, 4th degree tear through the rectal muscle, fistula infection 6 weeks later -- YUCK!). Amazingly enough, my second delivery was completely different. Another vaginal birth, same size baby with the same size head, and NO tearing or stitches at all, and pushed for only about 20-30 minutes. I was so relieved!!! Every pregnancy, labor and delivery is different. Don't worry too much about it -- your doctor will do what is best for you. Good luck!