"Gift" is good! Take the TheMightyHobie18, learn on it, and you can always transition to something else later on if you find it to be too much boat. Just take the advice given regarding staying in light wind until you're really comfortable, and always wear your PFD and appropriate clothing/wetsuit/drysuit for warmth. (How cold IS it in Oregon waters, BTW?)

I'm going to guess that if you're planning to solo often, you'll ultimately want to downsize a bit. (I just did.) On the other hand, some guys love the 18's and don't mind the gin pole rig to raise the mast, etc. It was just too much work for me personally, and it cramped my sailing schedule considerably to always have to line up w/ crew. But do take the boat, like I said, and you'll have plenty of time to work out your preferences in the future. You probably won't be soloing for awhile anyway if you're just starting cat sailing.