I checked out Orr & Griswold(2015) and can appreciate why you placed this to species rufiventris...due to the diagnostic and fairly conspicuous "bump" produced from the medial tip of the metanotum (their Fig. 7 for T. ensifera shows the case where the bump in lacking, and clarified the character for me). That character is apparently unique to rufiventris, and the range map shows the general Borrego Springs area as compatible with T. rufiventris (though T. pulchra is also compatible with the locale here).

As far as determining whether this is a male or female...I'm having a hard time distinguishing the antennomeres (getting both 12 and 13 in different attempts at counting ;-). But zooming-in on the full-size version of the image above, I think I can see a straight, narrow, black ovipositor (from lighting, positioning, and probability...I don't think it's a groove in the sand grain behind the terminus of the abdomen). And the shape of the tip of the abdomen seems similar to that in the female of T. ensifera shown in Fig. 7 of Orr & Griswold(2015).

Also, Orr & Griswold indicate the likely host bee for this cuckoo is associated with Phacelia, and there were loads of flowering Phacelia distans in the vicinity.

A neat genus...great to see it.