You can move the guide and the axis to the opposite position with the mirror attribute.
using Plots
plot(rand(10), xguide = "x", yguide = "y", xmirror = true)
guide_position can be used to only move the guide, however this does not seem to work perfectly - it cuts the label in GR:
plot(rand(10), guide_position = :top, xguide = "x")
Both images above are with gr(). This does not work with plotly(). I am not sure about the other backends.