Questions about visiting Cardiff

Hi, I'm ging to visit Cardiff in July, and I have some questions, any help isnhighly appreciated.

• how safe is Cardiff? I'm gonna arrive at 11 p.m. and there is a 1 km to my Airbnb, is it safe to walk alone at night, or do you recommemd a taxi or something similar?
• What's the best way to get around? I don't mind walking but would prefer something faster. Is there somewhere I can rent a bike for the week?
• How predictable is the weather? Is it safe to pack according to the forecast?
• I love trying local cuisine when travelling. Can you recommend any places to go to?
• Can you recommand anything to visit besides the tourist attractions I can find online? I'm especially interested in Music, electronics/comouter stuff and History.
• I assume everyone will understand english? Is it considered rude to just assume and just start speakimg english or should I ask if they speak english first?
• Any other general tips you want to add?