So, my 2010 Prius (~140Kmiles) has been getting progressively louder, the exhaust seems to be more visible, the engine doesn't stop running at lights/when parked and even slow speed drives (within parking lots ~10-15mph) seems to not use the EV exclusively. Is there any place in the CA bay area I can get the hybrid system thoroughly checked? Is there a Toyota dealership someone would recommend for this?
Exhaust leaks before the O2 sensors can wreck havoc with the way the car runs. It gives bogus info to the ECM/PCM and tells it that you are running lean if I remember theory correctly. If the O2 sensor senses a lean condition it will add fuel when there is really just an exhaust leak.
If you want to check the (two) oxygen sensors, there's a spec'd resistance range. You just pull off their connectors and check across a couple of the pins. Both are accessable from below. For the one downstream of the Cat you take off the metal shield just aft of the engine bay. For the one upstream of the Cat the Repair Manual says to tear the car half apart, but that's not necessary: it's easily accessable by just taking the engine underpanel off.
