As someone who spent a few weekends learning APL: no, the learning curve is not that steep.
The syntax is very simple, there's nothing scary about special characters if you can get over your fear of them, custom keyboard layout is absolutely not required (I've never used a custom layout for APL or Japanese or Cyrillic or Greek or any other non-latin characters that I type on a keyboard). Dialects are a thing but Dyalog is such an obvious choice if you want to learn APL that I wouldn't even worry about the rest. (K is worth looking into for its own sake but I don't consider it a dialect of APL; J might be a dialect worth exploring but so far it didn't impress me much and I found it much harder to read than APL).
One more thing: I find that reading APL is easier than writing APL.
The syntax is very simple, there's nothing scary about special characters if you can get over your fear of them, custom keyboard layout is absolutely not required (I've never used a custom layout for APL or Japanese or Cyrillic or Greek or any other non-latin characters that I type on a keyboard). Dialects are a thing but Dyalog is such an obvious choice if you want to learn APL that I wouldn't even worry about the rest. (K is worth looking into for its own sake but I don't consider it a dialect of APL; J might be a dialect worth exploring but so far it didn't impress me much and I found it much harder to read than APL).
One more thing: I find that reading APL is easier than writing APL.