You can force virtualenv to include a specific python version

virtualenv -p python2.7 env_name or virtualenv --python=/some/path/to/python env_name

You've made the best argument for using pip like this, however. Instead of having to install a virtualenvironment and install dependencies and all of that, you could just ship your program with the pip -t libraries, though you'd have to include the path somehow on the install so python knew where to find those files.