Yes, MgCl before food is best way, that s why I call it my "apéro"... I do this for at least 20 years with no problems. My Mg in erythocytes is above the maximum for labo tests, which is a relatively good indication.
I take about a gram of MgCl in a glass of water, 1-2dl with Taurine and vit. B6.
For potassium, I use citrate - 2 gr., it has no taste at all, there is one third of K, less than in KCl. I have tested pH, it is always about 8, half an hour later, that s not bad for the night s work for liver etc.