Please review my board design
Add reference designators to silkscreen (and several resistors in the schematic are missing refdes as well).

Decoupling caps should be close to whatever they are decoupling, not packed into a corner. Also, 20uF is a weird value, I'd switch both 20uF to 1uF low-ESR (ceramic).

If you're doing SMT for the USB connector and regulator, why not use SMT resistors and caps? Maybe even most of the diodes? You will have a much easier time putting the decoupling caps close to the things that need decoupling.

It'd be nice to clean up the right angle traces. Use 45º angles wherever possible.

Also, read the LM2596 datasheet, particularly the parts concerning layout. There are certain traces that should be shorter and thicker, especially your input cap and diode connections.