The lifts run from 9-4, the park is usually open from 10-10:30ish to 3:30ish. That's how it's been in the past anyway, I don't see much changing. The spring pass is 120$ this year and the cut off for the spring season is about the end of May though the last two years they've extended to the first weekend in June. There is no West Coast sessions this year so the park may not be as hyphy as in previous years since they always build it up for that.
Also I'm pretty sure Whistler runs their lifts normal schedule during the spring, it's 12-3 in the summer when it's only the glacier open on Blackcomb. At least this is how it's been the past few years. It may be only 10-4 or 10-3, but it's definitely not 12-3. Chances are you'll have to download there at the end of the day - depends on snowpack which I think they're doing alright on but the base usually melts out anyway because it's such low elevation.
I don't know how/if pass options have changed since Whistler was bought by Vail. I'm sure that a Hood pass is cheaper but Whistler's spring park has bigger jumps and for the most part better rails (less sticky), though part of that is weather dependent.