Hi Dee,
Humber Bay Park East is located south of the Park Lawn Rd. and Lakeshore Blvd. W intersection (in the west end, south-west of High Park and Bloor. There is a Park Lawn Rd. exit ramp off of the Gardiner only if you're coming from the west so take Lakeshore Blvd if you're heading in from the East. Go south on Park Lawn through Lakeshore Blvd when you come to the intersection. You'll find places to park on your right and I advise doing a loop of the whole park (its not very big).
Hope that helps, goodluck.
Iain