In the KC area (where I live), the Johnson County, KS suburban street grid is a western extension of the Kansas City, MO grid, and as such, the numbered streets all have a "West" prefix. However, in most cases, this "W" doesn't appear on the street signs. Among the major Johnson County suburbs, only Olathe and Gardner include directional prefixes on their street signs; most of the other big ones - Overland Park, Shawnee, Leawood, Mission, and Prairie Village among them - leave the directional indicators off. (A couple of the smaller municipalities in the northeast part of the county, such as Roeland Park and Westwood, include the prefix, but county-wide, it's more the exception than the rule.) Meanwhile, KCMO itself is mixed - signs for east-west numbered streets display prefixes, while named ones ( Linwood, Armour, Gregory, Bannister, etc.) omit them. However, north of the river, all streets with "N", "NE", and "NW" prefixes include them on the signs.
As far as other cities go, St. Louis doesn't include directional prefixes on the signs, at least not in the city; the county is more varied in that regard, with some suburbs (Clayton, Kirkwood, Webster Groves) posting the prefixes, and others not. In Denver, meanwhile, there is this weird inconsistency regarding the signs for the east-west avenues: "West" avenue signs include the directional, while "East" ones do not, for whatever reason. On the other hand, street signs in Chicago and Minneapolis always post the prefix.
From your experience, what is the practice of other cities throughout the country regarding how streets with directional prefixes are expressed on the street signs, as far as whether or not those prefixes are posted?