Greenhouse Orientation and spacing

Hello from PNW everyone!
Planning on some greenhouse/hoop houses for next year as season extenders for small market garden
Thoughts on a N-S orientation versus E-W.
Also, if E-W, how close can/should I put them? looking at 2-3 houses 20-30 foot in length
Thanks in advance for the help!

It depends on what you are growing in them, how warm it gets inside and if you need to, how well you can vent excess heat.  Hoop houses tend not to vent heat well unless you get the wind blowing through the open ends. Even then the middle areas tend to be a lot warmer than the open ends.  You might want to consider prevailing winds in your area more so than the sun in order to vent them properly.  Proper venting will help to control humidity which in turns helps to control plant diseases and other pests.  

In either event, you will want them far enough apart that they don't shade each other.  Since you aren't talking about cold frames, I assume that you are in a fairly mild winter area. I know here in Texas, where winters are often mild, a north/south orientation is typical so that there is plenty of solar gain all day but these are often used to mature a lot of things for early season sale.  

Width to length ration is probably quite important too when it comes to ventilation.