I had laser throughout last summer. I used sunscreen any time I was going to be out in the sun. It worked fine. I don't spend a lot of time outdoors anyway, and even more rarely in direct sun. If you spend a lot of time in the sun this might be different for you, but if not you should be okay.
Mind you, that's not going to change the policy of the place you get your laser done. But if you can talk them into doing it, you should be fine.