The rules, as stated on the US Embassy website, state that anyone who has ever been arrested (even if totally innocent) or convicted of an offence is ineligible to enter the USA under the Visa Waiver Program. (i.e. with an ESTA). So you're obliged to apply for a visa. (The USA doesn't recognise our Rehabilitation of Offenders Act, so no conviction can ever become 'spent' for US immigration purposes).
Theft counts as 'moral turpitude' which, under the US Immigration and Nationality Act, automatically bars you from entering the USA. So, in the first instance, the US Embassy would have no alternative other than to refuse you a visa. However your application could then be referred to Washington as an application' for a 'waiver of permanent ineligibility. If that was granted the US Embassy could then re-consider your visa application.
The minimum time to get a response to your visa application (where a referral to Washington is necessary) is around 5 months, but I've seen much longer times (up to 15 months) quoted on here by people who've actually been through the process.
Many people simply 'forget' about their convictions and enter the USA (illegally) under the Visa Waiver Program. The US authorities have no direct access to UK criminal records but they can be provided with such information in response to a specific request.
Chris