I wouldn't think it's worth it since the chances are so small that you'd get a ditto in one of the safaris.
(1/18) * (1/10) = 1/180
about (1/10, at most 1/12 for the number of Pokemon in each safari group)
Really small chances
I think I'm better off trying to get a Fcode from a ditton guy on friend safari .com
Thanks for your input