So what I'm asking is, would the methanol interfere with the MeNH2.HCl precip.?
Most definitely, methanol and xylene are soluble in each other, and as methanol is a very good solvent for both methylamine freebase and the hydrochloride, then this could interfer with precipitation.
If you have converted all the methylamine to its salt form, then you could vacuum distill off the methanol, and when it's gone, the methylamine hydrochloride will fall out, as there is nothing keeping it in solution.