There is no L in the Japanese language, but some Japanese can still say it with practice. If they cannot pronounce it properly they will most of the time use an R in its place. It's like somebody who cannot roll their Rs trying to roll their Rs, it's possible, but not easy and not natural.
That about says it, yes. If a Japanese person tries to just say "L", it usually comes out as "eru", while saying something like "lock" would come out as "rokku".
There is neither a 100% R nor a 100% L in Japanese, what they can pronounce naturally is a mild R most of times. If to give it percentage it's like 70% R 30% L, they don't say R with emphasis like other languages. Same goes with F and H (fu).