New To GIT have some (probably simple) newbie questions

Sorry if these questions seem simple but I am new to GIT, I've done some searching about how it works but I still have some questions that I hope someone on this list would be kind enough to answer.  I am using msysgit on Windows 7.

For some of my projects I have to comit changes to SVN.  So I did some research and found out how to use git-svn so I start by right clicking on the directory I want to store my repository in, and I select Git Bash Here.  I enter in the comand

git-svn clone -s --username=myusername https://mysvnrepo/svn git

and that works and it creates a local git repository that is cloned from the svn repo, then if I

git-svn dcommit

that keeps then synced up, but there is my first issue, manually syncing, so I look at git hooks, so if I create a file called post-commit in the hooks directory of my local git repo with the following content

#!/bin/sh git-svn dcommit

that should work to automatically sync my local git repo and the remote svn repo upon me committing to git right?

What I have no clue how to do though it to get this to work with another git repo, I mean I can use the gui to clone a git repo, but how do I sync them up.  The reason being is I use a git hosting service where I want to mirror all my commit to, just as a backup mostly.

How can I sync up my local git repo with the remote hosted repo AND where necessary svn using svn-git?

My final question is a matter of work flow.  I have a local it repos on my machine using msysgit, as well as hosted git repos with an online service.  Since I am a single developer its easy to just sync my commits back to the remote repo for each project I have.  But if I do get another developer or two to help me how does that work, do we all just sync to the one hosted repo or should we all sync with another too?  And if so how do I sync with multiple git repos.

Thanks in advance for your help.