Install the vips GUI, nip2, then try loading your JPEG image in that. Right-click on the thumbnail, select Header, and look at the fields displayed. You should see orientation in there.
I have Ubuntu 13.10 / vips-7.28.5 / ruby-vips 0.3.7 here and I see:
$ vips --version
vips-7.28.5-Sat Mar 9 18:46:42 UTC 2013
$ gem install ruby-vips
Fetching: ruby-vips-0.3.7.gem (100%)
Building native extensions. This could take a while...
Successfully installed ruby-vips-0.3.7
1 gem installed
Installing ri documentation for ruby-vips-0.3.7...
Installing RDoc documentation for ruby-vips-0.3.7...
$ irb
irb(main):001:0> require 'rubygems'
=> false
irb(main):002:0> require 'vips'
=> true
irb(main):003:0> a = VIPS::Image.new("pics/img_2522.jpg")
=> #<VIPS::Image:0x00000001a0e528>
irb(main):004:0> a.get("exif-Orientation")
=> "1 (Top-left, Short, 1 components, 2 bytes)"
irb(main):005:0>