The only way Luke on a speeder bike would make sense is if he and Obi-Wan have their conversation in Ben's hut. Then from there have him ride a speeder bike across Tatooine. With a lot of editing, that could be an ok possibilty.
But I would rather have a pretty CG scene of Luke flying in and across Tatooine. Like Obi-Wan and Grevious did on Utapau in ROTS. That would be much easier to do and alot more realistic.