Update 4-1-17: The canal frontage road is closed where the farm fields end (1.6 miles in). There is an irrigation ditch across the road and also a fence. You can't continue to drive on this road so we looked for other roads/ways to get there but didn't find anything. Since we weren't prepared for a very long day (i.e. walk from that point) we abandoned our attempt.
I made an attempt on 1/26/18 and can confirm that the road has been fenced over immediately past the irrigation ditch
(not even a gate!). It looks like there might be some nice dirt tracks on the north side of the range off Powerline road, will scout it out another time when I have more water with me in case of a long walk, and will post an update if the north side goes.
Thank for the notice. I heard from others that this approach has become difficult in recent months. It may be possible to come in from the south but following powerline tracks from Alamo Road, but I cannot comment further on that.
If you are able to get there, send along your notes and I'll update the page.