OpenGL: Probably, yes. iPhone development: no!
If you only have a week, don't waste it trying to get up to speed on iPhone dev! I have a friend and colleague who sunk months of time and over $1000 into becoming iPhone-proficient, and ultimately had to cut his losses and quit that line of work. He said Apple and the iPhone development community is just not that friendly to developers; people have more of a guarded, competitive attitude.
I myself tried Android dev, and was able to get their SDK and emulator set up, running and modifying a sample app, in a few hours. When I tried the same with Apple, I ran into signups, fees, and ultimately, being unable to get further because I don't have a Mac, and you can't develop for iPhone on Linux or Windows. (Maybe you have a Mac?) Another big barrier was that, IIRC, you can't run a program that you develop, on an actual iPhone, unless you first pay $99 to join the Apple developers program.
It's not my desire to start a flamewar... no doubt some have been very happy with iPhone development. My wife has an iPod Touch and I would love to write apps for it. I'm just relating my and my friend's experiences, and I would recommend only trying to invest time in iPhone dev when you have plenty of time to spend on it.
The main point is, if you want to learn OpenGL and do something simple but cool, within a week, that's a reasonable goal, and can be very rewarding. Try to combine that with learning iPhone and you are likely to be very frustrated.
The safest bet would be to first learn some OpenGL on a platform you're familiar with, whether that's MacOS, Windows, or whatever. See these SO questions:
Then once you've got that working, if you're especially interested in mobile devices, Android is more open (and free) to get involved with, and uses Java (iPhone uses objective-C). For that you might try here: