Here’s the simplest way to get the AWS CLI installed OS X El Capitan.  Disclaimer, I’m brand new at this so there’s probably a better way. Thanks to these three sites that posted the commands below.

Install pip:
sudo easy_install pip
Use pip to install awscli and ignore six since it keeps throwing an error on OS X 10.11 for some reason:
sudo pip install awscli --ignore-installed six boto3
Verify awscli is installed:
aws help
Set up the configuration profile. This requires an Access Key ID, Secret Access Key, Default region name and Default output format.  Instructions to obtain that info are here:
aws configure --profile agoodprofilename
Configuration settings should be located here:
~/.aws/config
~/.aws/credentials
Verify connectivity to AWS
aws ec2 describe-instances
Get the AWS Completer setup (way easier to use Tab to complete commands)
complete -C '/usr/local/bin/aws_completer' aws
Verify that Completer is working
aws ec Hit the Tab key and aws ec2 should appear as an option
Add Completer to your bash_profile
cat >> ~/.bash_profile
complete -C '/usr/local/aws/bin/aws_completer' aws
export PATH=/usr/local/aws/bin:$PATH

Hopefully you’re good to go at this point!