I think its going to boil down to your goals in the relationship and your comfort level. Going on a vacation with someone you aren’t really interested in making something work may not be a good idea. For one it allows you to see them in another light than just normal dates especially if you will be sharing a room. Its important for you to figure out how much time and energy you want to give this new relationship. The other flip side is that you can just see it as a good time and go and be fine. Again that’s where the comfort level is key.
I personally have not gone on vacation with someone who I wasn’t serious with. The man I took vacations with even though we had a split I ended up marrying. However I have friends who went on vacations with current boyfriends and it is what it is, a great vacation story and another place to add to your maps of visits. So unless you plan on dumping your girlfriend or not really attempting to vest time into her I would say stay home. If you plan on making it work and having some fun in the process I say grab your sunblock and have a great time. Memories are better even if they change when you are vested and are willing to make it one to remember. If you plan on being the type that is going to dump her when you get home, save her the headache and move on.