If you use a sunscreen and cover your face with a towel, then you will protect your Retin-A treated facial skin from the harmful effects of ultraviolet radiation. Irregular hyperpigmentation, wrinkles, skin growths, and skin cancers will be avoided! (What part of your body did you say you WANTED these things?)
I know; I like the "bronze beauty" look too, but you should get it from one of the brands of "misty" tan or "tan in a can" tanning lotions and then use the highest SPF sunscreen available as you look good on the beach, at the pool, or in the bedroom! Skin cancer scars, wrinkles, and blotchy, dark growths on your skin just don't look good, so why tan at all? Ultraviolet is BAD, and except for 15 minutes of sun exposure a day necessary for Vitamin D synthesis (or just take your vitamins or drink a glass or two of fortified milk!), you just don't have any reason to want to damage your skin's DNA. BTW, the damage that ultraviolet radiation does to skin is permanent and cumulative, which is why it takes a couple of decades for your skin to go to heck!
Oh, and the risk of fatal melanoma (the worst kind of skin cancer) increases with sun exposure or tanning booths. Contrary to tanning establishments' advertising, there is no GOOD ultraviolet, UV-A is just slightly less bad then UV-B!