I'm with the "Do It" crowd. I've got a son about your age and told him the same thing as he ponders his future. At this time he doesn't have a girl friend though. It's more fun to travel with someone with the same sense of adventure. There is nothing holding you down at this time, and believe me, once you have a job, children, mortgage, loans, etc. you will be limited as to what options you have with life. Granted, issues with health can come up and there are other things that can disrupt plans, but you're young and the percentage of you or your girl friend having serious health issues is minimal. You can still adjust to any other issues you might face. In addition, you will learn a lot about yourself and your partner as well as life in general by going out there and living it.
Many of us retired folk have said that life is backwards - we should be able to get out and experience the world when we were young and then settle down when older. Thankfully my wife and I are healthy and active in our early 60's and with retirement it has brought us the ability to travel and do other things we want to do within financial reason.
BTW, look for a Chevrolet if you can. I say this with humor. When I was young Chevy had a commercial jingle sung by Dinah Shore. The clicky below has a little background on the "See the USA in your Chevrolet" jingle.
http://www.vintagechevrolet.org/articles/VCO_2001019_dinahshore.htm Oh yeah, we're seeing the USA in our Chevrolet now. Enjoy your travels.