But on the other hand, finding the correct place to look for Leo I is rather easy.  Just center your telescope on Regulus and sweep due north by about 20'.  Use a low power eyepiece because Leo I is quite large and diffuse.

It's not clear to me what the minimum aperture is to detect this object.  I found observations by experienced  observers using 10 and 12 inch telescopes, but nothing smaller.

For many telescopes which suffer from stray light, the trick seems to be to use just enough magnification to place Regulus outside of the field and no more.  In my 18-inch I used 94x.  Regulus was high at the time, near transit, which aimed one of its large diffraction spikes right at the galaxy.  When I moved the scope north from Regulus I saw nothing but the glow for the spike.  Instead, I moved to a recognizable patter of stars to the northwest of Regulus and then swept to the east.  As I did this the glow of the diffraction spike appeared, but I also discerned a large oval shape blended into the glow from the spike.  This was the galaxy and once I was able to pick it out the first time ot was relatively easy to spot. 

Leo I appears as a large oval glow that is extremely diffuse -- no central concentration at all could be discerned and none of the stars were resolved, although I didn't attempt higher magnifications.

The field in an 6-inch f/8 at 50x.  North is down and east is to the right.