They made it a national monument, not a national park or wilderness area.
According to releases, this will allow MORE money to be spent making improvements to roads, campgrounds, etc.
"As a national monument, the San Gabriels will honor existing property and water rights, public access and rights-of-way for roads and utility infrastructure, administration officials said. Existing recreational activities — such as hiking, camping, fishing, cycling and panning for gold — will be unaffected."
from the LA times: http://www.latimes.com/science/la-me-obama-monument-20141011-story.html
As for Carrizo Plain, it is currently 246,000 acres of National Monument. Legislation was submitted to turn 60,000 acres into Wilderness area, about 25%. So, it won't be "locked up." One can travel and camp in wilderness areas. You just need to do it with your feet instead of your car. Currently, there is grazing and oil drilling leases in Carrizo Plain. I think part of the designation is to get rid of the current drilling leases. Previous drilling has turned up dry, but current owners are threatening to drill.
