This is the time of year the citrus trees start to ripen up around here as seen on the orange tree in our SJC garden. I'm not sure but my guess is this is a 'Valencia' orange that is primarily used for juice.
Orange trees require a significant amount of heat to sweeten up, which we don't really have here along the coast. 'Valencia' is one of the few varieties that doesn't require as much heat as long and so it is the one commonly grown in this area. The fruit will be fully ripe in the spring, but can stay on the tree without any deterioration throughout the summer, making it a "pick as needed" type of resource in the garden.
My favorite thing about the tree? That would be the amazingly fragrant blooms in the spring, reason enough to grow this tree that Orange County was named after!