I'm in the process of getting off the Depo myself (not to get preggers right away, but just being proactive for when the time comes). I have been off since December 2010 (6-ish months) and still do not have a normal cycle, even with the BC pill to help get me back to a normal cycle.
Chances are, you are NOT going to get pregnant within the first couple months of being off the Depo. The hormones used in this form of BC stick around FAR longer than with the pill - hence why you get a shot only 4x's a year vs having to take a pill every single day. Your body is going to take some time to "recalibrate" so to speak, and get back to a normal menstrual/ovulation cycle. This has been known to take up to 24 months, everyone is different of course - some take more time, some take less. However, it is very rare that a woman gets back to a normal cycle within a month or two. Talk to your doctor about your plans and see if he/she has any further advice for you. In any case, I would not be surprised if it takes at LEAST 6 months before your hormones have normalized enough so you can conceive.
Best of luck to you!