I wouldn't put anything in the vendor folder as that's where composer dumps packages. Like node_modules (if using node), I put bower_components at the base of the site (where artisan is and project-level config files). If not there, you could dump in the /public folder as those components are all front-end related.

So you are you putting your less/sass files in that same directory?

larvel/bower_components
      /less

I guess my main confusion is where is the best place to put your front-end dev files as they relate to them main laravel directory.

I keep sass at the base as well:

/app
.....
/public
/node_modules
/sass
/bower_components
bower.json
package.json
composer.json
Gruntfile.js

...but any setup would work, just probably not a good idea to put anything not coming from composer in the vendor dir as most people keep this out of their repos and just run composer in dev/stag/prod.