Eww-ww-w! That ground will not suffice!
Tips:
1. Route signals/power on top if possible (preferred routing layer). Only dip into the bottom layer if necessary (crossing under components, avoiding noisy areas, crossing under tracks, etc.). This keeps the bottom ground as solid as possible.
2. You don't need those big blobs around the pins -- cut down the 3.3 and 5.0V pours (or fills or whatever they are), or just remove them entirely (the pads have more than enough annular ring to support the pins themselves).
3. Bleh, why is the 3.3V reg even all the way over there? Madness! Shove that thing right by the connector, no need to run two traces all the way across the board!
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
4. Cfilt is on the wrong side -- it should be referenced to the output pin. You could shove over Cout and Lfilt a little to get the needed space, or shuffle things around a little so, like, Cout is left of L1, and L/Cfilt are where Lfilt-Cout are now.
5. You can afford to use
way more vias. Especially on U8, if it's going to need some thermal sinking. These can be via-in-pad (but mind solder wicking / thieving), or placed around the periphery of its tab (tented or otherwise). A via on the inside (under the pin, just above the pad) of U8 GND could be used. I like to stack a few vias in a row near large components (like Cin and Cout, and U8 as mentioned), helps reduce the inter-layer impedance of those grounds. And vias can just be placed kind of wherever to help better marry the ground fills (stitching).
Now... if you're planning on hand making this PCB, you probably do want to be stingy on vias, and that's OK. (You probably want to avoid top side soldered pins, too. The top and bottom blocks/fills/pours around your connectors seem to suggest you've already had this thought...) If you're buying, it hardly makes a difference in cost, at least until you get into seriously dense patterns (like "uncommitted prototype area" breadboarding stuff!).
As for the choke, another Lfilt would probably do. Make sure it's well damped, you don't want the switcher going cuckoo because you've accidentally made a (lower frequency) resonant tank on its input! This usually suggests small values (<1uH?), not enough to affect much LC filtering of the switching ripple itself, but it goes a long way towards knocking down those high frequency squiggles.
Tim