Mr Wes - Depending on where you are at with your photography learning journey, that 18 - 55 kit lens is a decent enough lens to shoot with. I found that it was great for daytime, landscape and general shots. I'm also shooting on a T2i.
What are you planning on shooting at Puerto Rico and what are you shooting at home?
If you want to shoot animals/wildlife on your holiday, then you are going to need to at least head into the 150 - 250 mm mark (or beyond) on the crop camera. If so, there is the canon kit 55 - 250 mm, which is still a kit lens; or if you have the $$$ of the 70 - 200 mm, f/2.8 IS.
If you are planning on shooting in low light conditions, then you're going to need to head into a lens with a wider aperture of at least f/2.8. At this stage, if you stay with Canon lenses, you're going to need to consider whether the longer zooms (variable f/3.5) is of more benefit to your shooting style or whether a wider aperture (f/2.8) is better.
If you don't want to replace the 18 - 55 kit with the 17 - 55 f/2.8, then you might want to consider adding prime lenses to your bag, for now.
For what it's worth, I started with the 18 - 55 and 55 - 250 mm kit lenses.
I enjoy shooting in low light conditions and in bright daylight. My style of photography is such that I'm taking shots mostly in the 30's mm range on the crop camera.
I bought a 50mm f/1.8 prime after about 6 months (because I was asked to take pictures at a friend's wedding) and I've now replaced the 18 - 55 mm with the 17 - 55 f/2.8 for those low light pictures.
For my style of shooting at the moment, the 55 - 250 mm is sufficient; but I have plans to replace it with the 70 - 200 mm at some stage when I start taking pictures for indoor sports or wildlife. Right now, I don't do much of either.
I've recently picked up the 10 - 22 mm Canon lens as well to extend my range at the lower end. I seriously considered getting the Tokina 11 - 17 mm f/2.8; but no one had it in stock. I figured that if I was going to use the UWA in low light, I'd set up the tripod and use different settings.
Good luck with your decision.
