I find myself in beautiful High Park for one of two reasons: to bring my dogs to run or to use as a photo-shoot location for engaged couples. As it can be expected it is crowded on nice days. Everyone else seems to have covered the picturesque areas so I'll just write about the dog stuff.
The off-leash dog park is just past the Grenadier cafe, where there is a brief two-way traffic zone. You can park along the right, and release the hounds as soon as you pass through the gate.
After they get the sniff out of their system we take to the wooded trails which according to Kafrey and Six, all seem to lead down to the creek and the paved road (Spring road I think). The off-leash areas are clearly marked and you will encounter signs telling you if you are entering or leaving an off-leash area. Inevitably, there is the odd dog-less person who wandered along, didn't see the sign and is confused at to why he is getting his crotch sniffed by a pack of dogs.
The dog-park part has a nice sandy surface, plenty of picnic tables for humans and a water tap that the city turns on in May. There are a couple porta-potties if you take the trail towards the allotment gardens, and lots of waste-bins for the dog-bags.
After a round in the trails and a romp with new friends your dogs will actually be asking you to go home.