We have looked at all types of signs over the last two decades, and our favorite is a simple aluminum with vinyl letters held up by two 4" x 4" posts sleeved in white PVC with decorative white PVC caps. It's not only among the least expensive, but it is arguably the longest lasting and cheapest to repair. We have our signs built at Fast Signs, which are nationwide, but our favorite one is in Overland Park, Kansas, and we typically have them shipped out of there. The only custom feature of our signs is a "notch" that is cut out at the top, which is an idea I stole from the old movie "The Philadelphia Story". These signs look fantastic when flanked by white vinyl 3-rail fencing. You can continue the theme throughout your park by simply installing wooden 4"x4" columns and sleeving them in white PVC with the same PVC cap, and then screwing on to them, in aluminum, everything from speed limit signs to street signs.