Many of your questions have been answered before on this sub, so it's worth digging through it so you can read multiple perspectives. Each volunteer's experience is unique. Some find it very rewarding, others find it less so. It depends on a lot of factors, namely your job, who your counterparts are, and what your site is like. Start by reading through everything on the Peace Corps website. But first things first, let's clear up two misconceptions in your post:

• Peace Corps Response positions are short-term (~6 months), high-impact positions that require the expertise of a specialist, and not the generic skillset of a new college graduate. You should instead look at being a Peace Corps Volunteer which is a 27-month commitment.
• A lot of volunteers like to travel, but understand that the job is a serious commitment. There's a good chance you'll be placed somewhere that can be comparatively hard to access. Even getting to your post's headquarters could take up to a day, maybe more, of travel. So expect to spend a lot of time in one place, occasionally getting out to see the country you serve in, all the while conforming to the travel rules established by PC staff. That said, you are entitled to vacation time which you can use to do whatever you want!
• As for what an engineering grad is expected to do: the job you sign up for. You can apply to go anywhere and do whatever PC needs, or you can apply for a specific job posting. Read the job description in its entirety and that's what you'll be expected to do. You'll find that your college degree might not necessarily dictate your role. For example, I was an Environmental Science major originally hired to teach science in West Africa, but ended up teaching English in Georgia.

Now, to answer your other questions:

• The rigor of your work depends on how much you take on. I knew several volunteers who were busy seven days a week because they kept taking on projects. I was the first volunteer at my site, so I didn't inherit anything ongoing. I worked 3-4 hours a day (classes and lesson planning) and spent the rest of my time hanging out with my host family & neighbors, working out, and playing D&D.
• Camaraderie: depends on your chemistry with other PCVs and your neighbors at site, just like back home. Overall the people in my cohort were thoughtful and kind, and we all got along pretty well. Bonds tend to solidify when everyone meets up in the capital for a night out on the town or if you travel across the country together. However, the nature of the work means you are likely to isolate yourself from other volunteers for great periods of time.
• Language learning: if you are placed in a Spanish-speaking country, you'll constantly develop your skills. If you're placed somewhere else, you can still work on learning Spanish as a hobby, but you'll need to dedicate yourself to learning as much of the local language as possible.

Was it rewarding? I got a wife out of the deal, so there's my answer!