running fabric script locally

Yes, you can run fab locally by using method local instead of run. What I do typically is have methods for setting up the environment, and call these methods first before calling the actual task. Let me illustrate this with an example for your specific question

fabfile.py

    from fabric.operations import local as lrun, run
    from fabric.api import task
    from fabric.state import env

    @task
    def localhost():
        env.run = lrun
        env.hosts = ['localhost']

    @task
    def remote():
        env.run = run
        env.hosts = ['some.remote.host']

    @task
    def install():
        env.run('deploymentcmd')

And based on the environment, you can do the following

Install on localhost:

    fab localhost install

Install on remote machine:

    fab remote install