We saw and posted about the same vintage photo series when it went live (see "Today's News" 5/16/2012) and were also blown away by images we'd never seen before. The one you're referring to we believe had not been published previously (the caption reads: "Not published in LIFE"), although there are equivalent images from the day published elsewhere. The tone of the original article is interesting in its cynicism, thinking that Las Vegas was already pushing its luck in 1955, when it turned out it would be several more decades before that became a reality.
In terms of your question, you can make out most of the casinos in the image from their neon signage. The photograph was taken facing west, so it's correct that the Golden Nugget is on the left, facing Binion's Horsehoe, with the Hotel Apache still atop. We initially thought that the 1955 date was erroneous, due to the big neon "Bingo" sign visible on the left. We assumed that to be Club Bingo, which didn't open until 1962, next door to the Lucky Strike Club, which opened in 1954, but it turns out that big "Bingo" sign was advertising the bingo at the Lucky Strike Club. In-between there and the Golden Nugget was the Nugget Saloon (which at first we took to be part of the Golden Nugget, but they were separate).
Across the street, the Boulder Club (1946-'56) was in-between Las Vegas Club and Binion's. And you can just make out the "Sal Sagev" sign beyond at the end of the street on the left, which dates this picture to 1955 (or earlier), since '55 was the year the Sal Sagev became the Golden Gate.
Beyond Club Bingo, on the same side of the street, you can see the Pioneer Club, with Vegas Vic, which opened in 1942, and beyond that the Monte Carlo Club, which later became Coin Castle. The open space at the end of the street is the future location of the Union Plaza, which opened in 1971 and today is simply the Plaza.
