You buy your insurance in your home country before you depart- assuming it's the US, then you buy it from a US insurance company. So yes of course they will speak English.
In terms of limits, I usually pick unlimited for medical, and $10k for travel/trip rebookingz as part of an annual policy. But for your own cover, think about how much you're spending on the trip.
Re medical, it's different for the US if you have your own US medical insurance - this may provide cover overseas as well. But consider whether you need cover for evacuation.