youth hostels

[BlueWillowPlate]

I am 54 and *still* stay at the occasional hostel, but sometimes 2-star hotels work out to be just fine--no pampering there, but the price is right.
Do your research beforehand...but only you will be the final judge. Check out the reviews at Tripadvisor, Eurotrip and Eurocheapo.
I've been fine at The Village in Paris and many hostels in Germany, where the standards are high.

[chielgirl]

Some hostels have age limits; bookings.com and hotels.com are additional avenues to research.
When in Italy and Spain and France, you can stay in convents.
They're clean, very reasonably priced and safe, no one's going to mess with a nun.
Some have curfews and many provide breakfast.