As far as the saddle goes, if they do not have bike lockers and you leave your bike out locked to the racks, to to your LBS, have them take the quick release out and have them put bolts in where you saddle is. It is harder to change seat position then, but it is also harder for someone to steal your saddle. They need an allen wrench then. You probably know where you want your seat, so set it and bolt it. Also, be careful when you lock your bike that your wheels, if they have quick releases, are locked as well.

I don't have quick release on my rear hub, needs an allen wrench to loosen so I just lock my front wheel and bike. Don't worry about the rear. If you do this, you MUSt carry an allen wrench with you in case of flats! One time I forgot