Yes, go into to app settings for wifi connections and tell Echo to "forget" the one you do not want to connect to; i.e. only have the 5G signal selected. (Of course, both 2.4 and 5G need to be two distinct SSIDs and not one merged one.)
I can't imagine why the 2.4 is not a good signal as good as 5G, you most likely are on a crowded 2.4G signal. If you know how to change the channel of your router, do that and see if things improve before doing above..