Hi cowpolyslo,
In Vancovuer, you always need to plan for the rain. No matter, it is March, May or July.
I was at a wedding in Cecil Green Park last July. I highly recommend it. It's beautiful. It rained in the morning

. Luckily it stopped just before the ceremony. They have a big pavilion at Cecil Green just behind the building. I think that they would have host the ceremony there if it continued to rain.
You can see a wedding video at Cecil Green at
http://www.lo2ve.com/client/kirby/hl.html
Good luck!
