They are reported to open mostly by fire but they also open in hot weather. You can tell they open without fire as most of the trees in residential areas are not the result of fire. The cones do stay attached for many years.
As I mentioned, these pines are a bit unusual and may produce 2 sets of cones in one year.
Other 3 needle pines in our area:
P. attenuata, Knobcone Pine is native to the northern county and can be seen in UCSC wild areas. Cones are very different, in large clusters on the main stems and held for years.
P. canariensis, much longer softer needles, longer cones, much fuller habit but more or less the same overall shape but way full.
P. coulteri, longer bluer leaves, more stiff and dont seem to droop on the stems, not as restricted to the ends of the branches as they last 3-4 years. Much broader habit. There are some around.
P. jefferyi, the cones are different in that the prickle on the scale is curved inward and will not stick you and you will not likely see one in SC.
P. radiata, covered earlier, dark green leaves, shorter and softer.
Interesting specimens can be seen everywhere, but you should to go see them at Point Lobos, with the mixture of the blue water and the cliffs, just remarkable. Don't forget to look at the Monterey Cypress on the cliffs as well. Go to Waddell Creek by the county line, the olds ones are covered with moss, and those that are still alive are pretty nice. Pinus radiata is susceptible to pitch canker that kills many of our trees.
There is a nice specimen on E Cliff in Capitola
In the south county there is a real survivor in the rail junction yard on Salinas Rd in Pajaro.