I'd also like to chime in against the 28-135. While I don't own it, I have used it before and while the images it puts out are okay, they're simply not great (in my opinion not significantly better than the 18-55 kit zoom), and on a crop body like the T3i, 28mm becomes 45mm, which is long enough that it may leave you feeling restricted even for street photography and group/environmental portraits, to say nothing of landscape and architecture (even if it's not particularly your thing, one of the defining features, I think, of what we call a walk-about lens is its ability to do just about anything on a whim).
I don't know whether the macro or walk-about is more important to you, but if you were considering the 100mm L macro, then the EF-S 17-55mm f/2.8 IS USM isn't too much of a stretch financially. I know you said you're planning to go full frame in a few years (as am I), but a few years is a long time, and the Canon lenses hold their value extremely well (if they didn't, I'd have bought all the lenses I ever wanted used by now...
), and if you're serious about practicing photography, it's a lens that won't let you down.
I've also heard good things about the EF-S 15-85mm f/3.5-5.6 IS USM, but I've never had an opportunity to use one and the fact that I almost never see people with them or trading them suggests they may be harder to sell when you do upgrade.
If you are set on sticking to only EF lenses, the 24-105L is of course wonderful, but for about the same price as the 17-55 you lose quite a bit in terms of performance on crop (it's also slightly heavier).
For macro, I would say that aside from a macro lens, lights are your friends. They're extemely useful for bringing out fine detail, creating aesthetically pleasing reflections, and whiting- or blacking-out your background. Canon 430EX IIs are nice, but on a budget Yongnuo YN560s can be had for 1/3 the price if you are willing to shoot manual (which is a good idea for product-type macro photography, anyway), and cheap radio flash triggers abound. Strobist is an invaluable blog for learning that type of lighting.
Just to put it into perspective, I don't know exactly how much power those flashes put out, since those figures are rarely published, but just as a for instance, if you were serious about studio product photography you might look into some studio strobes (monolights). The most modest of these run about 160 Ws (watt-seconds) and have flash durations in the realm of let's just call it 1/500 (even though this is maybe a bit generous for a low-end strobe, it makes the math easier).
Time for some dimensional analysis.
160 Watt * second 500
------------------------- * ------------- = 80,000 Watts.
1 1 second
So you'd need approximately 800 100W light bulbs to produce the same amount of light. Needless to say, a setup like that would both look and cost ridiculous.
Sorry, I seem to be rambling. I just get so excited talking about photography! You sound like you know what you want from your gear, which is more than many people can say, so I think you'll find the right decision even if it takes a little more research or thinking. Have fun shooting!