I drank it as is. Not to be recommended in cases of alcoholism, of course, but I find alcohol helps prevent the vasoconstriction that mescaline can sometimes cause. It may even help with absorption of the mescaline, and also is not without precedent if you look at some accounts of festivities in Real de Catorce, for example.
I do prefer a freshly-made cactus brew without alcohol but this was just how things rolled at that particular time. Boiling off the alcohol would be entirely do-able if circumstances permit. I'd say the trick is to ensure that the brew is concentrated enough (and known to be so) before considering using this preservation method. It would be best to be able to avoid having to consume an incapacitating amount of alcohol in order to get sufficient of a dose of mescaline. The other approach, which is the one I took, is to drink the huachuma liqueur slowly. This makes it gentler on the stomach and gives the body time enough to eliminate the alcohol without causing excessive intoxication.