From the US State Department:
SAFETY AND SECURITY: U.S. citizens traveling in Burma should exercise caution, register with the U.S. Embassy and check in for an update on the current security situation. U.S. citizens are encouraged to carry their U.S. passports or photocopies of passport data and visa pages at all times so that if questioned by Burmese officials, they will have proof of U.S. citizenship readily available.
In September 2007, the Burmese Government brutally cracked down on peaceful demonstrators, using gunfire, rubber bullets, batons, and tear gas against them and those observing in the vicinity. The authorities killed at least 30 people during the crackdown and arrested more than 3,000. On September 27, 2007, security forces shot and killed a Japanese journalist in the Sule Pagoda downtown area during a demonstration. The Burmese Government has a standing law, which is sporadically enforced, that bans all gatherings of more than five people.
On May 7, 2005, three large bombs simultaneously exploded in Rangoon at two crowded shopping areas frequented by foreigners and at an international trade center, killing at least 20 people and wounding several hundred. On April 26, 2005, an explosive device detonated at a busy market in Mandalay, killing at least three people. Although other smaller-scale bombings have occurred in Burma in recent years, including in early 2007 and early 2008, the 2005 bombings were more sophisticated and specifically targeted more highly trafficked areas than those used in other bombings.
In light of these incidents and the possibility of recurring political unrest, Americans in Burma should exercise caution in public places and be alert to their surroundings. Furthermore, Americans in Burma should avoid crowded public places, such as large public gatherings, demonstrations, and any area cordoned off by security forces. The Embassy also advises U.S. citizens not to photograph or videotape the military or police, because doing so could be interpreted as provocative.