Is there a waiting period recommended for getting Botox after Blepharoplasty? Only 3 weeks PO, but I'm anxious to get started

Your surgeon may choose to administer Botox at the time of surgery, if it is in a location that is distant from the surgical site, like neck bands for example.
However, if your question pertains to the crows feet area for example, depending on the extent of your blepharoplasty, your surgeon may choose to wait, or may choose to administer it at any other appropriate time, including the time of the surgery. Three weeks post op seems sufficient to me, but there are very few "absolute" answers in medicine. Like all things, the best choice is to discuss your concerns with your Doctor, who will be more familiar with exactly what was done in your case.

It is probably okay for you to have botox 3 weeks after surgery. Check with your doctor first to see if it is okay with him.