Most laser treatments require you to be out of the sun or very careful about the sun (hats and zinc sunscreens) for a month or two after treatment. If you live in a four season climate, the best times for treatments are fall, winter and early spring when the UVA is lowest.
If you live in an always sunny climate (lucky you!) then pick the seasons when you will be outdoors the least, and be very careful with sun or light exposure after your treatment. Your doctor should advise you. Remember treatments like Thermage, Exilis, etc are sound waves, and skin is not light sensitive after them. So you can do Thermage and Exilis any season.
See Dr. Irwin’s answer to a question about pregnancy and ingredients in skin care products.
See the SkinTour article on Skin Care and Pregnancy.