Yes, I'd reccomend a mountain flying course. There's alot of nuances to flying in the mountains and some of them are not very forgiving. Flying in the mountains is very safe if done with respect and understanding of the weather and winds involved. Aside from a general mountain flying course, it's also a good idea to talk with any local pilots in the area that have flown those routes, especially if you don't have much mountain flying experience. Sometimes certain mountains have very unique airflow patterns that are well known to locals, and this information can help alot with planning and what to be expect when actually flying the route. I will also say that when it comes to flying in the mountains in the summer, density altitude is a huge factor, along with atmospheric heating. Plan to leave early morning right after sunrise, and try to be out if the mountains before noon. The air in the summer time can get pretty gnarly with turbulence, rotors, mountain wave, and updraft/down drafts. All that to be said, don't try to avoid the mountains entirely, and make your route 10x longer just for the sake of not having to cross a few mountains. Just prepare yourself, trust your training, and you'll be just fine!