I just went to the spray tan place yesterday to get some info... I have been self-tanning for years on my own, but it's tricky to get the right coverage.
If you want to go that route (on your own), I do recommend exfoliating like crazy a couple of days beforehand, using disposable plastic gloves when applying, using a tanner with a bronzer so you can see where you're putting it, and moisturizing like crazy every day afterward. And if you decide to bring your self-tanner with you on vacation, remember to put it in a carefully-sealed ziploc because for some reason those things are prone to leakage/spillage and obviously they could make a huge mess on your belongings. I buy all of mine from a beauty supply chain, and use only those brands (not had as much luck with Clinique, or what they sell at
WalMart).
Not sure if I'm going to do it, but pretty sure I want to try it and see how it compares to what I'm doing on my own. Here they charge $35 for a full-body spray and it's supposed to last 5-7 days. They also sell a self-tanning product that I could apply while away to keep it going.
So to the OP, I haven't done it yet, either, but I think that since you don't really know how it's going to "take" on your skin and whether you will like how it looks as it starts to wear away, I would recommend doing it a few weeks beforehand as a test run. I know that will cost you more money, but I think in the long run it will give you peace of mind.