Ruirui,

If you take Calaveras Rd. east of Milpitas, it will take you out of town and up to Ed Levin Park. If you continue on Calaveras Rd. (looks like a left-hand turn) it takes you to Sunol. Or you can take Felter Rd. (looks like straight-ahead) you will climb and the road turns into Sierra Rd. There's a steep 4 mile descent to Piedmont Rd. Turn right (north) onto Piedmont and it will take you back to Calaveras Rd. Another right takes you back to the park.

SteveE