Park at the school bus turnaround then follow the road. At about 1.2 miles there is an obvious side road, you will see the trail as you start up that road. Just follow it to the falls. (and just when I thought DNR was run by Darth Vader they go and do something cool like this. OK, another chance).
Can you follow this to the top of Teneriffe? Yes, you can but don't count on it being easy. This is the old Mailbox Peak trail times two for steep and not maintained. At about 2,800 feet is the toughest part, a little scramble up some rocks which is easy when dry, a bit scary with ice. But who can complain about something new to try with 360 degrees of beautiful view and about .1% of the crowd on Mt. Si.
Now DNR just needs to construct a parking lot!