I’ve had Sprint for many years and have used it while travelling a number of places nationwide. I find drapped calls to be nearly non-existent. Though their tower coverage is not as extensive as other carriers, since they have a free roaming agreement with Verizon, I’m always able to use the calling features wherever I am with no additional fees (I have unlimited talk/minutes), even where there is no Sprint coverage. You just have to watch out for data roaming (which I disabled on my phone). The biggest concern I have is getting and maintaining a consistently strong 4G signal, but I have an older phone and the backup 3G works well for most online activities (and of course you can switch to a secured/PW protected WiFi signal as well). During bad storms, my WiFi (whether through Xfinity, AT&T, Dish, etc.) is lost fairly often and can, less frequently, be out for one to several hours… Sprint towers only lose signals due to weather once in a rare blue moon and get back online relatively quickly in such instances.
Of course, being CMDA, you’ll want to check to see if you’ll need other options for international travel where GSM is more prevalent. Sprint’s unlimited plans include data, text, and calls while in Canada and Mexico (and free calls to them from the US), but this free plan does not have that. It does, however, include the global roaming in 200+ locations that’s on all plans, although data is only 2G unless you buy a day or week of high speed data and calls cost ($020/minute), text messaging is free. If you need to make international calls from the US, you can add that for an additional fee.