I'm considering the Magic Lantern update for my T2i specifically for the AGC disable feature. Is there a way to actually monitor the audio from the camera? I'll be using an external mic.

Since there is no AV jack, that has not been done yet. There have been discussion, but no resolution that I am aware of.

ave your yourself the trouble and get a separate recorder ie. Zoom H1.
there are more reasons for ML but the preamps on the T2i suck even if AGC disabled.

You can see the levels on the screen, so at least you know you recording at something around the right level. At some point, they want to get the usb/av jack to monitor audio, but it can't be done yet without breaking usb function.

ave your yourself the trouble and get a separate recorder ie. Zoom H1.
there are more reasons for ML but the preamps on the T2i suck even if AGC disabled.

I do believe a second, separate audio recording device is always better but I have found that without an as separate audio operator it is a VERY complicated proposition. I'm not saying that it can't be done and that there's not a whole lot of people doing it that way right now but I'm personally so absent minded that I can be sure that at the end of a typical workday I would end up with a lot of footage lost to no matching sound because I forgot to press a separate record button on a separate recording device. That's why I got myself a Juiced Link DT454 even though I have a 60D, with the manual audio controls and everything: to have the ability to plug directly into the camera any pro-grade, XLR interfaced pick-up gadget, have the headphone monitoring ability, and the tell-tale audio level lights outside of the video monitor. Isn't good resolution linear PCM audio the same in a Canon body or in a Zoom recorder? The big difference is I don't have to sync it in post and, of course, a $120 lighter pocket!

By the way, I wanted to ask you guys that own Zooms, can you monitor the sound you're getting while recording on those things? Does the monitor reflect any variations you apply on gain?