lauraperezcerratoFeatured By OwnerFeb 12, 2013Hobbyist Photographer
I would go for the 28mm as you won't be getting a wide angle because of crop factor, as ~Mockingbirdkids already stated, but you will be getting something similar to 50mm, which is fantastic for learning. I wouldn't recommend picking up a zoom lens: you'll learn a lot more with a prime lens, and you can't beat the price/quality proportion.
My biggest advice to a beginner is to not invest a lot of money into your equipment until you've become more familiar with what you have. I think the biggest mistake a lot of beginners make, is they feel that a better quality lens or different optics will make their photography better. It's paramount to learn to work with what you have, and then upgrade your equipment to follow suit. (I made the mistake of buying above my skill level, and while I have some fantastic gear, some of it ended up not being what I really needed, and the funds could have gone to something more important.)
For some inspiration on what you can do with a basic Canon Rebel and a 18-55 kit lens, check out `zemotion's earlier work, as that's all she used:
If you do decide to get a lens, I second the Canon 50mm 1.8 lens, it's a very inexpensive lens, and will give you a wide aperture to experiment with.
Both len's are great as long as you realize the 28mm Wide Angle won't be "wide angle" on your camera because of the x1.6 crop. It'll be more like a 44mm. if you want to do some wide angle landscape stuff I would go for the EF 14mm 2.8L or EF 14mm F2.8L II or something that is a compromise ... like the EF 16-35mm F2.8L II
I would recommend the EF 50mm f/1.8 lens. These are very good and they are very crystal clear. Affordable as well. I got mine on sale for $110 instead of $125. It's a portrait lens and has a very good depth of field. With crop sensor cameras, the 50mm will be more like 85mm. The 40mm I hear is good for portability and weight, especially since you said you're going to do some travel. I'm actually going to purchase the 40mm here pretty soon, just so I can have it.