I've mixed alcohol with opiates before (I do not recommend this unless you are very experienced and know how a certain dose will affect you) and I'd say one or two drinks does not turn a safe dose into an unsafe dose even accounting for potential liver damage due to APAP. However, this depends a lot on what 120 mg of codeine usually does to you. Some people's "usual dose" is what they take in order to get really knocked on their ass and is most definitely not safe even by itself, let alone with alcohol. Nobody here knows if 120 mg is "safe" for you or not because we don't know your tolerance, only you know this.