We rely on our smartphone when travelling. Maps are great. You can download them so you don't need a connection, but it really helps to be connected to look up locations and such. We used the Verizon $10 a day plan in Curacao and ended up using 4 days of the 7 we were there, though it would have been 3 if I had not forgotten to turn the phone off. The resort WiFi was iffy and I needed to do some work and did use it for that.

The $40 a month plan is awful! We used that in Europe a few years ago before they added the $10 a day plan. You get 100MB of data and then pay $25 for each 100MB over that. We were not heavy users there, but still ended up with $50 in overages. And you have to turn the plan on before a trip and turn it off after a trip unless you travel regularly and want to pay $40 every month and you have to be careful that it is on for a month or they may prorate your data allowance and minutes and if your trip straddles the month ending you can end up with two months worth.