The DR-Z250 is a six-speeder. If you buy one, keep the air filter spotless, you lose 10-20% power when it is dirty. That makes a significant difference to the highway cruise and acceleration.
Don't worry about the -Z tag, it means nothing except to the marketeers trying to cash in on the "all new" DR-Z400's success. As far as I could tell, the bike was practically the same to at least as far back as 1995, probably longer, labelled simply DR250 or DR250S. Heck they didn't even update the plastics, just changed the stickers!!
Because the DR-Z250 was sold as road-legal outside the US of Eh? you could buy all the proper dual sport parts, bolt them on, and nobody would know it didn't come that way from the factory.
However I suspect they were road-legal in the US at some point. The one I had, was sent to Suzuki Australia, who complied it for use there, then it was shipped to Suzuki New Zealand who sold it new. So it had both AU & NZ compliance plates. Interestingly, the user hand book was for the American market, Suzuki Motor Corp USA or whatever, complete with all the road legal gear.