Yes, the bottom board of the peak of the porch. As long as numbers aren't too big in height. No one would have to squint from the street.

Wherever you put them make sure they are large enough and are clearly visible from the street so that in case of emergency the fire department or ambulance crew will be able to easily read them and find your home. I agree with the others, the front of the porch overhang appears to make the most sense from this photo. If you are sitting in your car on the street in front of the building where do your eyes automatically hit the building if you were driving through the neighborhood looking for the house?

What about something different like white numbers on the vertical face of the brick?

Definitely on the front of the porch overhang. Just wondering how the numbers would look in a frame that mimics the shape of the overhang.

Polly, my vote goes to black, or maybe a black, framed background with numbers in the same cream/beigh-ish color as your siding...at least it looks like that on my screen. Your side lights and window edges look white. If so, the numbers could also be white on a black background.

I kind of like the idea of spelling out the number, especially since it's fairly short. That I would just do in black. A nice script would be pretty, such as the 'Twenty Three' in this pic...

Numbers are always so much more practical.

I vote for black numbers. You also might want to consider some kind of lighting so they can be seen at night. There are some solar powered lights available to highlight house numbers so you wouldn't have to have extra wiring done by an electrician. Although I have to say I sort of like these back lit LED numbers like this image.

black, numbers, clear font, on the porch overhang. sometimes it's clarity over style, and this is one of those times.

Solar led house numbers:

Solar LED Address Numbers · More Info

Illuminated House Numbers · More Info

The site I found them on was http://surrounding.com/Products/Luxello/Index.asp it appears they can be powered by the same minor power as a doorbell, but yes they are wired and not solar powered. Solar ones are made - see Groveraxle's suggestions or just do a google of LED house numbers.

Etsy also sells many, many hand made home signs custom.