The Psyllid causes HLB not greening, Greening is carried by the Brown Citrus Aphid (that aphid dose not survive well in our area).
The Guava is, to this date a unproven redemptive measure.

HLB or Huanglongbing is the same thing as Citrus Greening Disease and it is (according to several sources) caused by the psyllid.
So far there has not been any Greening Disease or HLB found in Phoenix but the psyllids have been trapped in the Phoenix area.

http://www.ehow.com/facts_6752758_greening-disease-phoenix-citrus-trees.html

You are right, the guava is an unproven preventative but it is currently being experimented with and the fields with the guavas have had some positive outcomes.

Your correct,HLB is referred to as greening.
HLB can take up to ten years before it is noticed/manifested in a tree, one of the things that make it so hard to deal with, beside the issue that to date No one has found a pest management way of removing or stopping the psyllid.
Do you know how many psyllids have been trapped? and where they were found. I know that Yuma has been quarantined for awhile and I'm surprised this area hasn't been placed in quarantined also.

I haven't been able to find a number on the insects caught or on where exactly they were caught just that is was near Phoenix.
This was posted on one site.

If you have any questions, contact the Arizona Department of Agriculture, at (602) 542-4373, or California Department of Food and Agriculture, at (916) 654-0466.

On yet another AZ site, if you want to try the guava experiment they say to use one guava for every 3 or 4 citrus.

I am just waiting for the quarantine and like you am surprised that it is not in effect for here too.

Here's a recent notice from the Arizona Department of Agriculture.

The Arizona Department of Agriculture and the U.S. Department of Agriculture, its Animal and Plant Health Inspection Service are launching a campaign to help protect citrus against disease. The campaign, called âÂÂSave Our Citrusâ will coincide with the holiday travel season and remind people about the danger of sending uninspected citrus fruit and plants to friends and family.

In Arizona, citrus is a multi-million dollar industry and one of its most cherished symbols. Citrus is now being threatened by a disease that has destroyed citrus production in parts of the U.S. and across the globe.

Citrus greening or Huanglongbing (HLB) is the most devastating disease of citrus in the world. Infected trees decline in health, produce inedible fruit and eventually die. It has no cure, canâÂÂt be diagnosed until it is too late and is spread by an insect the size of a mosquito called the Asian Citrus Psyllid (ACP).

HLB has made its way through Florida and is now found in parts of Louisiana, Georgia, Puerto Rico, South Carolina and, most recently, in the Virgin Islands. Citrus greening has also been found in portions of Belize and on the east and west coasts of central Mexico.

In Arizona, the insect has been identified in 10 separate sites in Yuma County. However, none of the insects were carrying the disease and the disease has not been found in any trees in the Southwest U.S. The ADA has been able to control the situation with quarantine and other response actions.

For other answers to questions on citrus problems, try the link below.

Here is a link that might be useful: Diagnosing Home Citrus Problems