Okay – this is good – because there are some important points here. Remember that for brown spots the SPF doesn’t matter much as long as it’s at least an SPF 30. You want an SPF 30 AND a great UVA blocker. The SPF doesn’t tell you anything about UVA blocking. There are a lot of cheap (and expensive) sunscreens that don’t block UVA well. See this article on sunscreens and a list of better sunscreens. You’re right! You don’t want to invest time and money in laser treatments and then undo it with sun.
I recommend double sunscreening in places like Costa Rica. I use the Dermaquest 18% zinc sunscreen (either tinted or not) with the Colorscience powder layered over that. Or, a sport sunscreen if I’m in the water. I also used a brimmed hat as much as I can. Don’t forget to stop any Vitamin A creams (I use Renova) 1-2 weeks before your vacation. Also, in general, it’s better to plan your IPL treatments after sunny vacations, not before. Even with all of the above, you’ll still pick up a little color. Hope this helps. Dr. I