Thanks ultrarnr,
I think you totally correct about trying to predict the ship dates. The only good thing about the ship date aspect is that as a factor, it makes the option of waiting for the rebate more attractive. I.E., if the ship date ended up being in November it might not make much difference because the CA rebate probably won't be available until November anyway.
I just realized that I have short-changed Zero a little bit in laying out the 4 options above because I didn't figure in the tax credits, which could add up to another $1,500 off. (I tend to not count those because my wife the accountant usually ends up with any refund checks from the IRS.)
So the options look more like:
1) As mentioned, the MX option, costing around $11,383 - $1,500 (tax-related refunds) = $9,883
2) Buy the Zero S in August for a total of $11,225 (again before license and registration). Range more like 50 or 60 miles, speed more like 60 mph. Initial acceleration abilities not as sharp as the MX. $11,225 - $1,500 (tax-related refunds) = $9,725
3) Wait 4 months and buy the same Zero S and get a $1,500 rebate: $9,725 - $1,500 (tax-related refunds) = $8,225
4) Buy a Suzuki DR-Z400SM (that gets 65 mpg, goes up to 90 mph, handles well off-road) for $7,000 including tax and license and registration.
That brings the cost numbers berween the options more into line, though after looking through Ebay I am starting to think I could get the Suzuki DR-Z400SM for $6,000 rather than $7,000...