Can I test drive motorcycles from dealership in California even if you only have a Motorcycle Permit and a Class C license?

No.

Nope. First of all, most motorcycle dealers don't allow test rides. Second, those that do won't let you test ride without a motorcycle endorsement.

Yes, simple procedure- give dealer/ salesman full purchase price listed plus 10% to take test ride, you break it, you bought it. Bring insurance liability proof for $1 million also. After test ride, get most of money back minus 'rental fee' and processing fees.

I don't know of any dealer who will allow you to test ride a BRAND NEW motorcycle off their showroom floor. It's just not done. They MAY have a demonstrator bike that is SIMILAR to their new ones that you can ride, but even that will require you to have a license to ride.

ADDED: Sign up and take the Motorcycle Safety Foundation's basic rider's class... That SHOULD be enough to get the license in MOST states. (http://msf-usa.org/)

No. Must have an endorsement and even that may not work for a test-ride on certain bikes unless they are demos.

The dealer won't allow you to take their bike out on the road without a valid license

Not on the street, but in their parking lot. For a proper test drive you must be fully licensed for motorcycles.