Southland, I brought in a 07 Honda "Crotch Rocket" from Cali in 2009. I have been stopped over 10 times for MANY infractions (All of them my fault). I have never paid a peso of mordida and I have never gotten a single ticket!!!!!
I understand your position regarding cost and the condition of the bike. Mine had 500 miles and it was $5000. The same bike here in Mexico would have had been 7K with lots of brutal miles.
Having said all of the above, I would have to agree with Mainecoons. Having a Mexican plate is the way to go. I have tried to obtain Mexican plates,,,,,,BUT, right now most brokers want to talk "cars" rather than bikes. The fact that the bike is already here, makes it less profitable for them (transport fee).