Car rental LAX

[Vronsky]

Dear All,
I'm planning a roadtrip with my son from LAX to NYC next Summer.
Idea is to fly into LAX from Amsterdam, take three weeks to drive to NYC (southern route), and fly back from there. This means picking up a rental in LAX, and dropping it off in JFK or LGA

Do you have any recommendation for a rental company ?

Also, which cellular operator offers nation wide (LAX->NYC) data service ?

THANKS,
best regards,
V.