I wouldn't bother washing or waxing it, car covers let fine dust and pollen through all the time. So you'd only have to wash and wax it when you get back as well. If you go with a car cover you'll need a waterproof one and they aren't always lined on the inside, so you may need to get a lined one and a waterproof one as well and double skin it. I'd also buy a bag of longer occy straps and use these to hold the car covers on because they never have enough tie down straps on them and will blow off.
Your tyres and such will be OK, might flatten a bit but will round out again in the first few miles, you'll notice a slight patter patter and shudder until they do. Battery, as everyone says, disconnect it. Steering lock, disconnect the fuel pump and probably remove a front wheel and take it away, that won't stop the expert but will slow everyone down to the point where they'll look for easier pickings.
If you can afford it, go to Vinnies [or Clark Rubber] and buy three foam matresses/foam sheeting and attach these to the car with some of those occy straps, instant hail protection for under $50 or so.