don't go too late... 4-5pm is good...
and dont worry about drinking in public.. as long as you're not being blatant about it, ie getting mad drunk, pissing on cyclists and passing out on public bench's, it will be fine.
me and gf have had a lunch picnic whenever the weather cooperates on weekends, nobody bothers us when we sip on some wine...
canada is different than the U.S.
some cops are playa hatas