I pronounce it Lay-Low. I think I saw a company video with that pronunciation. Before the video I thought it was Lee-Low. I have never heard anyone pronounce it Lello- I like the sound of that. I just might switch.
I watched videos on Lelo products at EF just so I could figure out how to pronounce it! The trouble is, most lay people seemed to pronounce it lee-low, so that's how it stuck in my head. I should've watched the Lelo company sponsored videos first. =p