I suck at singing and playing at the same time.

It's a phase like everything else and will pass. We've all been there and with practice it will all fall into place. Practice the guitar part untill you can play it without thinking and then play with the song going a few times, add a few words here and there when you feel comfortable with it and after awhile you'll be singing all the way through it. Pick the song that you know best and stick with it! In a few weeks you'll wonder what the big deal was in the first place Best of luck! -Pix

keep trying!!!!!!!

Thanks for the advice...what's a capo?

I'll ditto the capo advice as well. Getting a song into a key that you are more comfortable with will certainly help and you'll be able to sing more confidently.

As far singing and playing at the same time...I've always found it helps to tap my foot. It helps me keep the strumming rhythm better. The other thing I do is use the most basic strumming pattern when I first learn a song. Down-down-down....(or you could just strum at chord changes too) It doesn't sound great at first but it gives you a chance to learn the chord progression without having to make real quick chord changes. Once you've mastered the progression and found the right key (with a capo), you'll be able to start to feel the rhythm of the song and the strumming will come natural. Keep after it, I'm sure you'll have dozens of songs that you can confindently belt out in no time!

sing along to songs that you like, you will find that some sound better when you sing them, this is your key.
also listen to a range of bands and again sing along, you will find some of them also sing in your key
tonyblue

well glad i wasnt the only one with this problem at first. it took me a while thou. i agree wit alota the ppl above. u just gota try wht diffrent things till u get it. like humming before singing, or tapping your foot, or foucusing on one more then the other. it always helps to learn the guitar part really well first so that your comfertable wit it. and yes capos often help find ur range too. lotsa diffrent ways but just keep trying! youll get it good luck and best wishes to ya!

Making the song easier to sing via a capo is a good idea. The best thing I was ever taught about music was in our high school band. I played trombone, and our director was a funny, very gifted musician...He also had a temper, which in many ways was good because he'd get the best out of us.
His big thing was.....TAP YOUR FOOT....He hammered that into us, if he saw someone NOT tapping their foot, a eraser, or some other non concussion causing projectile  would often be seen flying through the air towards the guilty party!! lol...Once I began playing bass, due to tapping my foot I had a better meter then most the drummers I worked with...not an ego thing, drums and bass are as one, or are supposed to be to create that foundation music needs.  Not that I was special, learning to tap your foot over time keeps you in rythm, it becomes automatic.....some drummers drove me nuts!  And it works wonders for all instruments..To sing and play at the same time is a process all it's own, but start adamantly tapping the foot to the beat now....learning good habits are far easier then getting rid of bad habits. The foot tapping is a GREAT habit, especially if the vocal seems to conflict with the guitar rythm. Playing bass and singing "Brown Eyed Girl" by Van Morrison was a challenge when I began playing bass. Van the Man sings on the backside of the beat, hell he sings on the front side.....tapping the beat with my foot made it much easier. Thats but one song, theres soooo many..You'll get it, what seems like a mountain now needs a stubborn attitude....that mountain will shrink....you will never quit learning, thats the beauty of music....Onward Thru The Fog!
Oh, I have two Jay Turser guitars, a beautiful acoustic which I will put against my 56 Martin D-18 anytime, and a Turser copy of a Gibson 335....it is awesome for what it cost me. I recently played a Martin D-28, looked gorgeouys..won't tune! Then I have played an old cheap harmony guitar which Sears used to sell that lacked tone,,but it tuned! A guitar that wont tune simply needs legs screwed on it, makes a neat coffee table. No two are the same. Turser is making nice stuff at a great price though.

To add to Stormside - tapping your foot is good IF you have a way to know that you're tapping it in beat.  In a band, you have a conductor who helps to keep the beat.  On your own, you don't have that luxury.  One thing you can do at first to help you is to get a metronome.  A metronome is the number one best thing to use to help you to stay in beat.  It won't help you sing any though.  But what you can do with a metronome is to start a song you know veeeeeeeerrrrrrrrryyyyyyyyyyy sssssssssllllllllloooooooooowwwwwwwwlllllllyyyyy and as you get it down, you can bump up the speed and still sing in pitch and on beat until you get it to a speed that you think sounds good (which is not always the same speed that the original recording artist did it). 

- Zurf

Worst thing you can do in music is to stand stock still. Whether you tap your foot or sway like a loon you are physically getting with the beat. Metronomes can really help. The more you internalise a regular beat the better.

The exception is old-style folk music where the meter is highly variable for dramatic effect, but even there you need to know what the rules are, don't kill the pace to make the words easier.