Jon Daniels has confirmed that Yu Darvish is in the Metroplex right now, in order to "gain a better understanding of the area and get a first-hand look at the operations of the reigning American League champions."
The deadline for Darvish signing is still a ways away, and negotiations are apparently ongoing. He's not here to sign a contract or announce a deal, however.
The Rangers won the exclusive rights to Darvish when their high bid of $51.7 million was accepted by the Nippon Ham Fighters on December 19. Texas has 30 days in which to work out a deal with Darvish, and if they fail to agree to a contract, Darvish's rights will revert to the Ham Fighters, and Texas will not have to pay the $51.7 million posting fee.
I would not expect a deal to be done or announced until right before the January 18 deadline. The contract amounts being bandied about generally seem to be in the five year, $60-75 million range.