I live by the ocean north of L.A. where smog isn't an issue. Its a runner's paradise... hard sandy beach at low tide, bluff trails, parks and mountains. For those who like to run on asphalt, there's lots of quiet roads and subdivisions. My favorite running routes are a variety of mountain trails on the front ridge which start just above sea level, ending up on the ridge top at between 3000 and 4000 ft altitude. There's the reward for all that toil and sweat, a wonderful view out over the ocean and on the clearest days with an offshore santa ana breeze, where the visibility is unlimited, all the channel islands can be seen
.. but it can be hazardous.. gotta watch out for mountain lions (rare), rattlesnakes (occasional) and downhill bikers with bad attitudes (commonplace). One of the the things to remember in summer, especially when doing a long run when its hot, is to take plenty of water... you can't have too much. I stash water on the way up under a bush at a recognizable landmark... it lightens the load for going up the mountain, and its there waiting for you (in theory!) on the way down. I learned about not taking enough water from bitter experience as few years back.. I got dehydrated and felt really ill for 24 hours.
I had some great advice from a sports physiotherapist re. training shoes: don't ever buy discounted "last years" or "discontinued" lines, because the chances are they have been sitting on the shelf or in a warehouse for up to a year, by which time the shock absorbency of the soles has diminished to a fraction of what it was when the shoes came off the production line. That 75% discount on an expensive pair of running shoes looks too good too pass by ... but it's a false economy. Numerous runners get injuries from trainers that are past their best, either as new (or having been used for more than 500/600 or so miles).
If you are in mountain lion country and you happen to encounter one... Stop running. Make yourself appear as large as possible, move to higher ground than it (if possible) wave a tshirt around, make as much noise as you can, throw rocks at it, be as aggressive as possible. It will more than likely dash away. They don't like Mace etc. either! Whatever you do, don't
try running away from it! If you encounter a bear...that's a real problem... its probably best to play possum and hope it'll ignore you..
And for the girls who run, I would always advise carrying pepperspray or similar. I haven't had any incident in 12 years since I started running, or occasion where I needed it, luckily. But its best to be prepared, just in case. Also, I always take my cellphone, whether I'm going for a 3 miler round the local park or a 15 mile slog on the mountain trails.
Just my 2 cents.