I planned on doing a gap year before university, only to realise I really don't have the money to do the things I really want to do (stay in one country for at least a few months, instead of a few days due to hostel prices soaring out of the roof) and I've already done three years at college so I'm heading to university this year instead. I'm 19 myself and I'm not worried about going to university late, I know lots of people of different ages go.
It depends what type of person you are, if you have the confidence at 18/19 to go and explore the world, along with the money, then go for it. You don't have to worry about getting into a job when you get back, you have university to look forward too. If you're eager to get your degree out of the way, then travel afterwards, lots of people do it and lots of people travel to places a lot whilst at university due to the opportunities that come up (you can study for a year in another country at another university). Usually people afterwards get a bank loan to go travel the world and do lots of activities and see lots of places, a few grand on top of a 40 grand debt really isn't going to make a difference in the long run, you'll always be paying the darn thing back unless you earn huge amounts. Plus with the advantage of adding to the debt, though it's not wise, you do get to travel the globe which is vital to some people, like myself. Living is now, you're only young once, see the world when you're fresh and have lots to learn, the career and paying back the debt can come later on in life.