My hemoglobin A1C is 5.3. Is this a good number for BBL surgery?

That is likely within the normal range for the lab, but you can confirm this by looking at the paperwork.

Dear UNDECIDED40,your HbA1c level is within a normal range so you should be able to get a BBL surgery. I would suggest you to discuss this with your plastic surgeon. Daniel Barrett, MD, MHA, MS 
Certified, American Board of Plastic Surgery  
Member, Am. Society of Plastic Surgery

If the result of your blood test is within normal limits for the lab used, then it should be ok to move forward provided that you have medical clearance.