@om_henners' suggestion will work well, especially if you are creating the grid in the "right" way.
The right way views each grid point as being offset from an origin by the sum of integral multiples of two basis vectors. In projected coordinates a good choice of basis vectors for a triangular grid consists of one arbitrary vector of the desired length (e.g., 9 meters) together with a rotation of that vector by 120 degrees. For example, if you want the bases of the triangles to be horizontal you can pick the first vector to be e = (9, 0). The second one would then equal f = (-9/2, Sqrt(3)*9/2) = (-4.5, 7.794229). Letting O = (Ox, Oy) be the coordinates of the origin, all other points on the grid are of the form
i * e + j * f + O
where i and j are integers. Here's the punchline: to compensate for the distortion in geographic coordinates, divide the first coordinate of each basis vector by the cosine of the latitude, convert all offsets to degrees, but otherwise everything else remains the same.
For example, at latitude 40 degrees the cosine is 0.766044. This converts e to e' = (9/0.766044, 0) = (11.74867, 0) and f becomes f' = (-4.5/0.766044, 7.794229) = (-5.874333, 7.794229). Now convert these four coordinates to degrees: division by 111,111 (meters per degree) is usually close enough. Using these vectors instead of e and f in the grid formula, but keeping O at the same location (and using the same sets of i and j values) lays out your grid in geographic coordinates. Over these short distances (up to 144 feet in this case, or out to several kilometers in general) you can get extremely high accuracy by first adjusting the latitude to a spherically-equivalent latitude before computing the cosine, but typically the error is so small (much less than 1%) that it doesn't matter.
The vector approach is illustrated in an old article of mine.
BTW, a nice feature is that you can easily rotate and shift the grid. To rotate it, just rotate the original basis vectors e and f by the desired amount, adjust their first coordinates by the cosine, and then recompute the grid points as linear combinations of these adjusted rotated basis vectors. To shift the grid, just shift the origin O. Thus you are no longer a slave to the coordinate system: you can orient and position the grid as needed for the application. Another nice feature is that every mathematically possible regular grid can be constructed this way. Just change e and f. For example, when f is at 90 degrees to e you will create a rectangular grid.