I lived in San Diego county for many years. There are a lot of rattlesnakes, even in populated areas. A lot of dogs get bitten by rattlesnakes. Even dogs who are not harassing a snake can get bitten. They might not even notice the snake, but if they get too close (e.g., while chasing a rabbit), that's it. This is extremely serious, $600 is getting off very easy. A small dog does not have much chance of surviving.
I think the vaccine you are talking about is "Red Rocks", it seems to be safe, but there is no evidence regarding efficacy. Here's what the UC Davis School of Veterinary Medicine has to say about it:
http://www.vetmed.ucdavis.edu/whatsnew/article.cfm?id=1883
It is derived from
Crotalus atrox (western diamondback) venom. The western diamondback is not found in San Diego county. It does occur in Imperial county though.
There are 3 species that are found in western San Diego county, 2 of which are common:
C. ruber (red diamond) and
C. oraganus (Pacific rattlesnake). The speckled rattlesnake (
C. mitchelli) is the least common (in coastal SD). If you go into the desert, you may also encounter the sidewinder (
C. cerastes). Each species has different venom. Although they have similar mode of action to the
C. atrox venom, it is not clear how effective Red Rocks is against the venom of these other species. As someone previously posted, Red Rocks known to be ineffective against the Mojave (green) rattlesnake (
C. scutulatus), because the venom has a completely different mode of action (primarily neurotoxic).
Many of the people that I know who hunt or herd with dogs do get their dogs vaccinated with Red Rocks as a "can't hurt, might help" measure.
Most people I know bring their dogs to rattlesnake avoidance training. This teaches the dog to actively notice and avoid rattlesnakes. This prevents the dog from harassing snakes, and also prevents incidental bites. I have used and can highly recommend
http://socalrattlesnakeavoidancetraining.com/ They do use multiple local species of snakes, as well as juvenile snakes (no rattle) and shed skins. You should avoid trainers who claim to use "defanged" rattlesnakes rather than muzzles, because fangs grow back very quickly (and also because this is cruel to the snakes). It is also important to be sure that the dog avoids the scent, not just the rattle sound, for several reasons: juvenile snakes do not have rattles and often inflict the most serious bites because they cannot control the amount of venom they inject; adult snakes can lose their rattles; selection pressure favors snakes that do not rattle and go undetected, versus snakes that rattle and get killed.
After avoidance training, my dogs had multiple rattlesnake encounters and never got bitten.
IMO one of the best things you can do is understand rattlesnake behavior and activity patterns and use that knowledge to reduce the likelihood of encounters. In southern California, rattlesnakes are not active when the temperature is below 60F or above 90F. In warm weather, they are active at night. Inland, overnight lows are almost always below 60F, and for about 9 months of the year it almost always goes below 50F. I got into the habit of running the dogs before sunrise to take advantage of the cool temps and avoid snakes.
BTW, there are rumors that Fiesta Island is free of rattlesnakes, but I have seen buzztails out there with my own eyes. Never believe that anyplace in rattlesnake country is snake free.
Here is a great resource:
http://www.californiaherps.com/snakes/snakesmaps.html
And here is some additional info:
http://www.vetmed.ucdavis.edu/vmth/pharmacy/pdfs/pharmnewsvol4-1.pdf (note that this incorrectly lists
C. viridis as occurring in Califoria, this is incorrect and should be
C. oreganus).