Weed is subjective, it really depends on your smoking habits and how you react to it normally. I smoke weed heavily, so when I trip, it is more of a route or a comfort thing. It doesn't change anything really. For others, it can completely change the experience. Follow your gut.
I love solo tripping. Tripping in groups, so much is going on that sometimes you can't focus on your thoughts. Walking about by your self with your brain can be a real experience on LSD or any psychedelic. When I dose on anything, I usually can't sleep until I have been at baseline for a few hours, so I am normally the last man standing while everyone else is crashed out. This gives me a nice alone period even when I am tripping with people. I usually go on a walk solo, and it ends up being a wonderful way to end my trip and reflect.
If you know yourself enough on psychedelics, and your comfortable with the dose, 300 mics isn't too much to wander around a nice semi-public place. For someone who has never tripped before, I would say that is unwise.
Things to bring in a small backpack: water, fruit/food/snacks, some petty cash, toilet paper, flashlight, music. Tobacco and several xtra lighters if you smoke. I bring a phone in case of emergency, but I make sure it's off, and in the bottom of my bag.
i carry a backpack when I am tripping away from home, because I like to have amenities, and pockets get sooooo confusing for me on higher dose psychedelics. I usually end up taking everything out of my pockets to find something, and losing everything I was carrying by the end of the trip.