Yes, they are next to essentially the same body of water (the Pacific Ocean), which then becomes known as the San Francisco Bay and the Carquinez Strait...
And yes, they are both in California...
What else?
Well, this is pulled right from the Wikipedia entry for Martinez:
Martinez is one of the only two places in the Bay Area--the other is the Golden Gate Bridge--where the Bay Area Ridge Trail and the San Francisco Bay Trail converge. The Bay Trail is a planned recreational corridor that, when complete, will encircle San Francisco and San Pablo Bays with a continuous 400-mile (640 km) network of bicycling and hiking trails. It will connect the shoreline of all nine Bay Area counties, link 47 cities, and cross the major toll bridges in the region, including the Martinez-Benicia Bridge. To date, approximately 240 miles (390 km) of the alignment—over half the Bay Trail’s ultimate length—have been completed. The Bay Area Ridge Trail ultimately will be a 500+ mile trail encircling the San Francisco Bay along the ridge tops, open to hikers, equestrians, mountain bicyclists, and outdoor enthusiasts of all types. So far, over 300 miles (480 km) of trail have been dedicated for use. East Bay Regional Park District's Iron Horse Regional Trail will join the Bay Trail along the waterfront, and the Contra Costa Canal Trail threads through the city from Pleasant Hill to the south.
When I read that my town is a kind of crossroads of this kind, it made me go "WOW". It also made me try to imagine what the sign post will look like where these trails intersect (as far as I know there is currently no sign anywhere in town)
I am personally very excited to be able to run or bike across the Benicia bridge!
For an overview map of the Bay Trail, check out http://baytrail.abag.ca.gov/map.html
For an overview map of the Bay Area Ridge Trail, check out http://www.ridgetrail.org/trail/map.cfm. The page http://www.ridgetrail.org/trail/trailtracker.cfm has a link to a trail tracker PDF (http://www.ridgetrail.org/trail/trailtracker.pdf) to track which parts of the trail you've visited.
