Thanks for your response. I have mostly used the Econ and know what you mean about struggling and sluggish-ness. When it's up to speed and the cruise set, it shouldn't be a problem.Hello and welcome. I would say that is the time to try out the econ button. Supposedly it's good for long stretches of highway driving. The car will struggle on hills in my opinion based on trying out the button in my hilly area, but for long stretches of highway you may see some improved mpg using it.
Good luck and enjoy the trip. I'll be going to Florida late August but not driving.