It might be easier to park your MH in a location that's less likely to have nefarious people around. Not always possible, I know, but campgrounds tend to be places with little theft going on. As others have said, it's very easy to pop the latches on outside storage compartments.
If you have anything really valuable, look into having a safe installed inside your MH.
2011 Rockwood Signature Ultra Lite 8293SS, 12K Equal-i-zer
2016 Ford F-250 XLT SuperCrew, 6.2L, 4x4, 6'9" bed, 3.73
2010 Rockwood Roo 23SS (2012 - 2014)
2009 Ford F-150 XLT SuperCrew, 5.4L, 4x4, 5'6" bed (2012 - 2016)