I lived there, on my own, in the 90s. It's my second favourite city after London - though Rio wins on beaches 😄
It's about as dangerous as any major city; the difference is the type of danger, I guess. There are a lot of robberies. Although there's plenty of major, gang-type crime in Rio, street crime's almost all poverty related (this is the same throughout Brazil, and in many other places with severe inequality). I used to keep a tenner's worth of cash in a front pocket, so I wasn't rummaging around in my bag for drink or snack money, and I'd keep it topped up. When I was robbed, I'd hand over this money. I viewed it a direct form of taxation!
The only visitors I've ever heard of having problems with actual violence are those - usually men - who 'have a go' if accosted.
Normal tourist advice applies. Sure you can wear watches and jewellery - cheap ones! Keep your wits about you and a firm grasp on your bag. Take your time, be open to experience, don't treat the place like a theme park. Avoid things like dark alleys.
Your experience will improve in direct correlation with the amount of Portuguese you can muster, not least because scammers target English speakers (they'll assume you're American, btw).
July & August are mid-winter. It'll be cool, overcast and a bit wet. There probably won't be any beach events at that time, but I wanted to stress it's okay to go to night-time events on beaches and to beach bars. It is unwise to wander on the beach after dark, though. You're absolutely fine out in the streets at night: if you stayed in all the time, you'd miss loads of local colour! Of course, Brazilians love kids.
If anything scary does happen, yell at the top of your lungs. If you should need the police, push for the Tourist Police who are used to our forrin' ways and much less likely to rip you off.
The food's fabulous. Fruit juices and vitaminas - fresh fruit milkshakes - from street stalls are wonderful; the same stalls sell green coconuts (coco verde) with the top lopped off and a straw to drink the juice 😊
I LOVE the Copacabana Palace! I could never afford a room there, but used to hang out at the pool and bar.
Go! Boa viagem! Divirtam-se bem!