I didn't have a rough time at all, but a lot of friends did not enjoy Paris because they found the people rude and unhelpful. This was absolutely not my experience, but this has been repeated to me so many times that I think there is some truth to it.

A lot of travelling solo is about self-sufficiency and also realizing when to ask for help. So if you're intimidated by the process, going somewhere where the people are pretty jaded by tourists might not be the best? However, I also think it's pretty great to have one of your first major travel experiences be in such a beautiful interesting city like Paris. Just set your expectations.

Definitely use tripadvisor to feel places out, but what about hostels? You are 20, and hosteling would be a fantastic way to meet other young people and other solo travellers.

Pickpocketers are very real, but just be smart about where you keep your belongings. Split cash and cards around your person. Never keep it in, say, the outermost backpocket of your bag. Just things that are clearly easy to jack when you're in a crowded subway car. I definiitely have had multiple pickpocketing attempts pulled on me in public transport- it's really not hard so be aware of your surroundings.

I would probably take like 100 pounds, but use ATMs and try to really get a credit card that doesnt have foreign transaction fees (though I don't know if this even matters within the EU). Call your bank ahead of time to know where ou'll be on what dates. I really think it's better to keep your spending electronically, but have cash as a back up.

Everyone I met in Paris spoke English to some degree, but if you're hitting up mostly tourist sites, EVERYONE will speak English. But knowing some french would be helpful, some of the train signs were all in french and confused me a few times.