You can only cache 10 maps though afaik, which for driving around Europe isn't really enough.
You could stop at places that have free wifi though, get something to eat/drink or whatever and download some maps. This obviously wouldn't be ideal however.
You could also just use data to download maps, I can't imagine that they're very big so it shouldn't cost that much (obviously you'd want to make sure you disable sync on other apps so you don't accidently use it).
Depending on whether you're going to be using your phone for calls/texts you could get a PAYG sim card (probably easiest getting one here, as I have no idea whether one from the country you're in would need to be registered or how difficult that would be as a foreigner) and chuck some credit on it (make sure roaming is enabled before you go, as some can't be enabled out of the country) as that would probably be cheaper than buying a decent sat-nav app with European maps.
You can normally get decent sized data bundles (if they're just being used for downloading some maps) for fairly cheap, I'm sure someone else will know decent bundles or the cost for data bundles on your network and at how much data you'd be looking at using (roughly).
Edit: Just got the market update on my phone. I hadn't bothered downloading it separately as from the pictures it looked worse than the old market, now it's installed I can't help but feel it's worse than the old market

.
I'll leave it installed for a bit and see how I feel, but I'm guessing I'll end up going back to the old one.