Of course, this is just one metric that you should be thinking about -- definitely not a metric that can tell you if you should buy or sell a stock on its own. Instead, do the calculation and consider why the price to free cash flow is what it is. A low number is generally pretty good, but not if there's a scandal brewing or a recent recall has cropped up that may cost the company a lot of money in the upcoming months and years.
Since free cash flow is a backward-looking metric, any significant changes in the business's operations will take time to be reflected in the price-to-free cash flow ratio, which can create a false sense of security.