Translation:I will take the elevator.
To use does have it's own verb, being つかう, but のる is being used here. In that sense, to take would be a better English translation because (well me personally) "to ride" isn't used much when talking about an elevator or escalator. Take used in this way also doesn't have a Japanese equivalent as far as I know.
Like Yuri said above, "noru" means to ride, not only elevators but cars, buses etc. It doesn't imply any direction. Like "will you take the stairs?/no, I'll take the elevator".
"Oriru", I think, in an elevator context, would tend to the "getting off" sense, rather than the "descend" one (unless duo starts using more kanji).
In natural English maybe, but it wouldn't be a correct translation of のる, which means to ride. The reason why "take" is a possible answer instead of "use" is because "use" has its own verb in this context, being つかう. As far as I know, Japanese has no translation of "take" in this context.