Building on the earlier suggestion, Sigma is solid but you should also consider Panasonic since they are part of the same alliance and tend to be very reliable. Before looking at specific glass tho, do you need autofocus for this trip or are you okay with manual focus lenses? Zion has some tricky light and you might not want to faff around with manual rings while hiking. If you want to stay under that $500 mark and keep things simple:

• Panasonic LUMIX S 20-60mm f3.5-5.6 L-Mount. This is basically a kit lens but the 20mm wide end is great for landscapes. Its weather-sealed which is huge for Utah dust. You can find them used for like $350 all day long.
• 7Artisans 15mm f4.0 Wide Angle L-mount. This is a manual lens but its very wide and very cheap, usually under $300. Personally I would stick with the Panasonic for the metadata and autofocus. Its a safer bet for a big trip.

Unfortunately, finding quality autofocus wide lenses for the SL2 under $500 is almost impossible. Most native options in this price range are not as good as expected, and I had issues with cheap adapters dropping connections in the past. To get decent results at Zion without breaking the bank, you should look at fully manual native lenses:

• Samyang 14mm f/2.8 MK2 L-mount
• This runs about $400. It is sharp in the center, though the plastic build feels a bit cheap.
• TTArtisan 21mm f/1.5 L-mount
• Costs around $230. It is very compact, but you will notice some soft corners unless you stop it down to f/4 or f/5.6. Going manual takes some getting used to, but for landscape shots at Zion, you can basically just set the focus to infinity anyway.

You should definitely look at Sigma! Their L-Mount Alliance partnership makes them a safe and reliable choice. Any wide lens they make is amazing and youll love the fantastic results!

Great info, saved!