Summary: A good time to get the annual shots is October or November, before the flu season begins.
Influenza shots are definitely recommended for persons with HIV or immune deficiencies.1 They are often given in October or November, before the flu season begins.
Where can you get the shots? A good place to ask is where you usually get health care.
If that doesn't work, a number of drugstore chains and other organizations have a traveling flu clinic that goes from store to store. These may be available only once at a particular location, and will usually charge a fee, often about $25. The two we checked, CVS and Walgreens, have online locators to find a site near you; many only give shots once, as early as October, so it's a good idea to make plans early.
Note that people with HIV should get the flu shots (not the FluMist nasal spray, since that contains a weakened live virus and could be dangerous for persons with immune deficiency; it is only approved for healthy people between the ages of 2 and 49). The shot does not have live virus, and cannot cause the flu.
In some cases, anti-flu drugs are recommended for people with HIV who are likely to be exposed to someone with the flu.1
In the U.S., the proportion of people with HIV getting the annual flu shot has risen "from 28.5% in the 1990 to 41.6% in the 2002 influenza season"2 -- improvement but still short of the U.S. government goal of 60% by 2010. In comparison, in countries with near-universal healthcare, up to 92% of people with HIV get the shot.2
Incidentally, the 1990-2002 figures were published in July 2007; it takes a while for the wheels to turn in U.S. medicine and research. A way to deal with this problem is to use real-time data centers when possible.
The U.S. Centers for Disease Control and Prevention has a flu information page, www.cdc.gov/flu/. It links to a page of information for persons with HIV, www.cdc.gov/flu/protect/hiv-flu.htm (last updated September 19, 2007 or later, despite references to the 2004-05 influenza season).
Gallagher KM, Juhasz M, Harris NS, and Teshale EH. Predictors of influenza vaccination in HIV-infected patients in the United States, 1990-2002. The Journal of Infectious Diseases. 2007; volume 196, pages 339-346.