GPS tech (Garmin, Hammerhead, Wahoo, RWGPS, etc)

I'm not sure if this is the correct place to ask, or if this has already been covered but...

I'm planning on going to Italy for some light touring this summer and would love to have a turn by turn gps system for my route. Is there an appropriate (an not too expensive) cycling option, and/or would it be possible to use a car gps system or do those cut out if you go too slow? I don't care about candence monitoring or heartrate etc, I just need something to tell me the way.

thanks

Probably the cheapest option is something like the etrex 20 or etrex legend with openstreetmap.
http://www.handtec.co.uk/satnav-gps/outdoor-gps/garmin-etrex-20-010-00970-10.html