My solution for setting multiple conditionals based on several variables in nginx. nginx doesn't allow for nested if statements, if/else, or any advanced logic, so this is what I came up with.

nginx_multiple_conditions.conf

# explain what I'm trying to do
# Given base domain of abc.com
#  1) typical visitor will type in abc.com
#     our SEO people want standardized www.abc.com all redirects are 301
#  2) issues in our environment have template assets pointing to 
#     http://abc.com/skins/some.css
#     This makes the browser redirect nearly 15 times, not good.
#  3) We want only the admin area to be https. Due to insecure pixels and other assets 
#     the rest of the website wouldn't load if it was all https. 

#Set all my tracking variables to N for false; this is string, not boolean.
  set $isSecure N; 
  set $isSkin   N;
  set $isAdmin  N;
  set $isNaked  N;
  
# Set to Y if the client is already in https
  if ($https = on) {
	  set $isSecure "Y";
  }

# Set to Y if the request is part of the assets we don't want to redirect
  if ($request_uri ~ ".*/(skin|templates)/.*") {
    set $isSkin "Y";
  }

# Set to Y if we need to redirect for SEO purposes; should not redirect template assets
  if ($http_host = abc.com) {
	set $isNaked "Y";
  }

# If the client is in the /admin area then make the connection secure
  if ($request_uri ~ "^/(framework/)?admin") {
	  set $isAdmin "Y";
  }  


  # If it's a naked domain and NOT admin, and NOT skins, then redirect to www for SEO
  # http://abc.com/          would be YNN
  # http://abc.com/admin     would be YYN
  # http://abc.com/skin/     would be YNY
  # http://www.abc.com/admin would be YYN 
  set $testNaked "${isNaked}${isAdmin}${isSkin}";  
  if ($testNaked = YNN) {
    rewrite ^(.*) http://www.abc.com$1 permanent;
  }
  
  #If it's admin and insecure, redirect to https
  # http://abc.com/admin would have been previously redirected to http://www.abc.com
  # http://www.abc.com/admin   would be NY
  # https://www.abc.com/admin  would be YY
  set $testAdmin "${isSecure}${isAdmin}";
  if ( $testAdmin = NY ) {
    rewrite ^(.*) https://www.abc.com$1 permanent;
  }

# I don't need to test for anything else as the logic handles itself from here. 
# If I need to add more tests I can just concat the other tests and test against that.
# Hope this helps, if you have a better way; I'd love to hear it!