The HIV infection rate in Namibia is about 25%.
Namibia's medical system is modern and capable of attending to whatever needs you may have. Staff are well trained and so HIV transmission in hospitals is not an issue. This applies to government and private hospitals alike, though line-ups are often shorter at private hospitals, and there have been cases of incorrect diagnosis in government hospitals.
The northern part of Namibia is in a malaria-risk zone, so consult a doctor before leaving, and take appropriate malaria precautions when travelling in these areas.
Namibia's water supply is usually safe to drink, except where labelled otherwise. Campsites next to rivers often get their water directly from the river, so do not drink it!
Having said all this, make sure you consult a physician specializing in health issues of Southern Africa, as well as things like the Centre for Disease Control (http://www.cdc.gov/) web page. Make sure you satisfy yourself of the safety of anything you're getting into.
Major Indigenous languages include Oshiwambo, Herrero, Nama, Damara, various San languages,and Silozi.
English is the official language and is widely spoken. However, the majority of older Namibians those educated before independence speak English only as a third language; therefore, the standard is fairly poor. English is more widely spoken in the north, as it was adopted as a medium of instruction earlier than in the south. Older Namibians in the South are more likely to speak Afrikaans or German.
Afrikaans is spoken by many and is the first language of the Coloureds as well as the Afrikaners. English is spoken as a first language by the remaining English families, and German is spoken by the Namibians of German descent, who tend to be in Windhoek, Swakopmund and various farms scattered through the country. German is one of the leading commercial languages as well. Portuguese is spoken by immigrants from Angola.
Namibians are very proud of their country. It is a well developed country albeit still a developing nation with all the modern amenities and technologies. Namibians have been exposed to a surprisingly wide variety of peoples during the United Nations supervising of the elections, as well as from various volunteer organizations. They are not offended by Westerners wearing shorts, nor by women wearing pants. It is not uncommon to see Afrikaners with thick, knee-high socks keeps snakes from getting a good bite and shorts walking about. It is customary when greeting someone to ask them how they're doing. It's a simple exchange where each person asks "How are you?" or the local version "Howzit?" and responds with a correspondingly short answer, and then proceed with whatever your business is about. It's a good idea to do this at tourist info booths, in markets, when getting into taxis, even in shops in Windhoek though it's normally not done in some of the bigger stores in the malls.
Namibia's country code is 264. Each city or region has a two-digit area code. When calling long distance within Namibia, prefix the area code with a '0'. Mobile phones are very common and run on the GSM network, using the same frequency as Europe and the rest of Africa. There are Internet cafes in Windhoek, Swakopmund and Opuwo, and hostels often have access as well.