A lot of people get tattooed while on vacation as a souvenir of a memorable time. There is nothing wrong with this provided that you can take adequate care of it while you're there. As previously mentioned, keep it out of sun and water while it's healing- so get any swimming or tanning out of the way first and watch out for sunburn.
More importantly, thoroughly investigate the shop in which you'll be getting your tattoo and the artist who'll be doing the work. I cannot stress this enough. There are a lot of really good artists out there but for every shop that is in it for the art there is at least one that is in this field only for the money. I've spoken to a lot of people who've been tattooed on vacation only to return home and find that the tattoo turned out to be much less appealing than their expectations. Tourist traps know they don't have to deal with touch ups for you if you're five states away. I know that sounds terrible, but unfortunately it's the truth. This is a permanent investment on your body. It's better to be safe than sorry.
A lot of good establishments and artists may be booked out for quite some time. If you know you're going on vacation and there's that one special artist in that locale by which you'd really like to get work done, call to set up an appointment well in advance. Several weeks or possibly months in advance. You already know you're going on vacation. They do not. Make sure your plans are set ahead of time. When you get to your vacation destination, stop in to the shop if it's possible just to touch base with the artist or establishment to finalize any plans. Then, go enjoy your vacation and get tattooed AT THE END OF YOUR VACATION. That way you can enjoy yourself and not have to worry about caring for a tattoo... and you still go home with an amazing souvenir.
If you know you'll be getting tattooed at the end of your vacation, it's imperative that you keep from getting any kind of sunburn!!! Also, remember to eat a good meal about an hour before you go in for your tattoo and remember to drink plenty of water. Dehydration isn't fun. :D
Think before you ink, and have fun on vacation. ;)