I take it you have never taken these before?
Before mixing drugs, you should be well-versed in all the drugs you are using. I suggest taking one and seeing how you react before mixing the two. You can catch a nice buzz from 1 soma alone, without the alcohol.
If you took all 5 soma's at once (which is not smart), you will more than likely be unable to function and/or pass out. Adding alcohol to the mix, will only increase the drowsiness and effects and is only recommended to do if you have a history with soma and know they react to your body. The combo can indeed be fatal due to CNS depression and other things to those naive to the drugs.
My suggestion to you would be to take one of those tonight, and see how you feel. The come grad night or whatever, you can gauge if you want to drink for the night or take a soma or two.
I don't suggest mixing the two, as it appears you have little to no experience with them, plan on drinking a 'fair amount', and yes it can be dangerous. Just drink some beer and bang some chicks and save the soma's for a rainy day, or the day after while you nurse your hangover.