Yes, take bear spray if doing any type of hiking in Yellowstone or outside in Shoshone or Custer National forests; however, make sure it is:
- EPA approved bear spray
- Is a decent size container
- From a reputable firm
- And you read on how to use it.
(And before the jokes come, I have used it, and it works, and know a few park and NF rangers who have use it and it worked.)
Here's a decent link to read, that covers the four big sellers...
Best Bear Spray Reviews | BestPepperSpray.net
Some other decent reading on use....
I have carried UDAP, and Counter Assault. Counter Assault is what I used in so I know it works and it has the largest container.