I would use virtualenv. Create a new virtual environment on the instance with 2.8.0 and make sure that you tell virtualenv not to use the system-installed packages. I'm pretty sure that is the default behavior but, just in case:
$ virtualenv --no-site-packages test_old_boto
Once the virtualenv is created:
$ cd test_old_boto
$ source bin/activate
and then install the old version of boto in the virtualenv:
$ pip install boto=2.2.2
and you should the be able to test things out.