Dealers carry insurance for test rides. If teir insurance covers a learner rider, then there's no reason they'll refuse. Of course, being able to prove basic riding skills would be a benefit!
As for test rides/drives, I ride till I'm convinced. If the dealer suggests I take it around the block, I'll walk away. When I bought the VStrom, I knew I would need the bike in city traffic, open roads, twisties and of course off-road. Well, you can't exactly go off-roading on a test ride so, my test ride was about 20 minutes in the city and between cars then, out of CT on the N2 and then riding the M62 towards Hout Bay. In total, I was gone for about 50 minutes - and I stuck in 10 liters of fuel.
Good luck and I hope you enjoy the test rides,
Cheers
Lawrence