YES - You should be able to work AO-51 with your HT!!!
Some general comments for working AO-51...
The two primary modes of operations for AO-51 are FM analog voice and 9600-baud packet. AO-51's transmitters have a variable power output, and can operate as high as 8 Watts output on 70cm. Amateurs are successfully working the satellite with handheld radios.
In one mode, the UPLINK (to AO-51) frequency for voice is 145.920MHz with a 67.0Hz CTCSS tone. The DOWNLINK (from AO-51) frequency is 435.300MHz.
First, you need to know WHEN and WHERE the satellite will be passing over your location. There are several computer programs that will tell you. In the home office, I use Nova for Windows. Outside, though, I use PocketSat on my Garmin iQue 3600 PDA. Both programs are easily updated with current satellite tracking data that is available on the Internet.
Or, you can go to... http://www.heavens-above.com
...and sign up. Using your longitude and latitude coordinates, you can access amateur satellite pass information (and a lot more!).
The one "absolute" for success is to open up your squelch. Working satellites starts off as a process of finding weak signals, so don't expect the satellite to be anywhere as strong enough to break squelch like your local repeater. I know it's noisy, but that's part of the process. Noise can also be an aid in locating the satellite because when the frequency starts to exhibit QUIETING, that's a sure sign that you are hearing the satellite, and you should get ready.
Use a good antenna for your handheld. A good gain whip antenna (like Pryme's AL-800) will make the difference. Using an Arrow dual-band handheld antenna is better, and if you prefer to homebrew your antenna, Alex Diaz XE1MEX has an excellent Yagi-Uda design.
Set up your radio so you can to tune for the doppler effect. Start listening 5 KHz above the center frequency - you will hear the satellite sooner and clearer. When you hear the downlink signals get scratchy or fuzzy, tune down 1KHz at a time, and reception should be clearer. Follow the signal down in frequency as the pass continues.
Don't hold your whip antenna upright. Vertical antennas are not good, and a HT held upright isn't either. The satellite isn't on the ground (which is what HTs and vertical antennas were designed for). TILT IT about the same amount as the satellite's ELEVATION. This means that if you are FACING the satellite, tilt it down towards the ground from HORIZONTAL an equal amount. If the satellite is to your back, tilt it up an equal amount away from the satellites position off the vertical. You will be surprised at the difference.
Some hams use headphones - especially if working full duplex. If you have a full duplex HT (like an Icom IC-W32A) you can listen to your own downlink (a good thing). Your brain is far better at discriminating signals than most expensive DSPs.
Knowing your gridsquare - and having a gridsquare map - is a quick way of identifying locations of what you will be hearing. The ARRL and Icom have some dandy gridsquare maps, the latter of which are free at most amateur radio stores.
Remember the "three Ps" for working amateur satellites: preparation, planning, and patience. Not every pass is workable with an HT or listenable with a scanner - so don't go after the 10 degree passes. Pick your passes, and work the ones you know will give you the best chance.
When you hear others, try to find a break in the action, and announce your callsign, grid square, and op mode, like this:
"KILO-SIX-LIMA-CHARLIE-SIERRA, D-M - ONE-THREE, handheld."
Many hams record their sessions for later review. Even if you don't make contacts, it helps to accustom yourself to the callsigns, voices and personalities of the other operators. When I first started out, I found it more valuable to know which contacts I missed rather than the ones I made.
Ask questions! Find an elmer or look up the AMSAT area coordinator for your area. Posting specific questions on the AMSAT bulletin board will also help you find answers.
Clint Bradford, K6LCS