I don't know about the safety of eating MSG, but it's not much fun for me. Small amounts tend to upset my stomach, larger portions provide nasty headaches.

I've recently tried a handful of pre-packaged freeze dried meals from Mountain House and Backpacker's Pantry, none of which listed MSG as an ingredient. A few of the meals for sale did list MSG, and I passed over those. Some of the meals I've tried listed "natural flavors" as an ingredient, which I've heard could include MSG, but so far I haven't experienced any of the discomfort I usually associate with MSG from eating those meals.

(I've always thought that if a flavoring was really natural, the ingredients would tell you what it is, instead of what it does.)