Yes, there generally are cabs readily available at all park entrances and at the resorts. For all but the MK, cabs will be close to the main entrance. At the MK you would have to take a ferry or monorail to the TTC and catch a cab there, or take the monorail or walk to the Contemporary and get a cab there. From WS at Epcot you would need to exit the park and walk over the the Beach Club or to Boardwalk to catch a cab.
I'm not sure how cabs work at CBR specifically, however, as the check-in location (where you would get a cab at most resorts) is completely separate from the buildings where the rooms are located. I can't imagine cabs are waiting outside each building or anything like that.
IMO, cabs are a viable option especially when going from resort-to-resort as there is no direct Disney transportation in most cases (the monorail end Epcot area resorts being the exceptions). Otherwise, you probably would do just as well with Disney buses.
