I have an HPS streetlight in front of my house that has a large "7" near the lens. Can anyone tell me what this means if anything? I have seen these numbers before. It not a location identification number, the pole that the fixture is attached to has that number.

Lamp power

7 = 70W
15 = 150W
and so on

Exactly. The large 7 is probably on a yellow label. The colour of the label indicates the lamp type. Yellow or shiny gold is HPS ; blue, MV, red, MH and if I remember correctly, green is LPS (or SOX). Large wattage lamps have a multiplicator. This means that 1000 watts is written X1. These are established by the NEMA (National Electrical Manufacturers Association) in the USA. They set the standards mostly in North America.

The reason why the label is up there is so maintenance crews can bring the correct lamp when climbing poles to relamp. Other people wanting to know the wattage and type can also determine this if they know the "code" !

Mine has a 17 on a blue label indicating a mercury vapour of 175 watts.

Yep, you just discovered the "NEMA tag" commonly found on streetlights
Blue is MV, yellow/gold is HPS, red is MH and I think red/white is PSMH.
Dunno about LPS, LED, or induction...
Also the number on the tag is a tenth of the wattage with the exception of 35w, 175w, and 1000w. I've seen both 35 and 3 for 35w, and 175w is 17. 1000w is X1.

Just did a quick Google search, and found more information on the subject on this Wikipedia page. Interestingly, it mentions wattage labels and colours for LED and induction lamps. It is quite a long article, but the labeling section is in the middle.