Travelling to America next February, However, one of the party has a previous conviction (UK), what does that person need to declare prior/during travelling to the USA ?
Potentially they need to apply well in advance for a visa - this will involve an interview at the US Embassy in London for which they will have to supply their police record.
It would be advisable not to book until they have their visa - depending on what/when they did whatever it was there's a chance it will be refused.
My husband had a driving conviction over 10 years old and had to apply for a visa ( drink driving). If it is a criminal conviction you will have to apply for a visa and go for an interview in London and depending on the conviction you MIGHT get a visa so don't book anything until you know. It cost him overall for hotel, court papers, something from the police and such about £400, so it's not cheap.