Layout on double sided pcb
It is always a good idea to separate parts of the circuit with different supply voltages into different areas on PCB. While pretty much mandatory for high voltages and optically isolated circuits it is less common for small voltages and slapdash DIY projects.

In your case I'd prefer more defined areas and no 5V surrounding 3V. But your PCB is quite densely populated, so I understand why the layout looks like that.

UPDATE

I just realized that ACS712 is current sensor. I would recommend changing the power lines on the left:


Remove those tiny vias. Keep the traces on one side. 
You can move all through-hole connectors (including those in other areas) to the ground side. This will simplify soldering.
If you do not want to move connectors then make transition to ground layer directly at the connector holes. If you do not have good plating on those holes you can add large pads around them stitched with several vias.
Shorten the traces. Ideally current sensor would be inserted into one wire only, the other is left off the board. But if you want both terminated at least put connectors close and with pass-trough pins facing each other, for shortest possible trace.