As always in Tango Argentino, music is the key: depending on the vals you hear, you might hear different rhythmical patterns.
I totally agree with the simple approach to only walk on beat 1 of a measure, especially since the valsecitos can get quite fast.
However, I would apply this with caution to steps like the cruze ("Step No. 5"), or generally when feet meet or lock in a tight cross. Such steps would normally stop the flow and create a pause. On the other hand they lend themselves to making use of one of the remaining beats, especialy if the music suggests such a short stop there.
To give you a musical example: listen to Anibal Troilos "Romance de Barrio" (with Floreal Ruiz singing). In measure No. 3 (as well as in 4, 5, 6 and 7..) we can hear the first two beats, followed by a pause (on 3). This may be interpreted by the dancer as follows:
On 1: normal fluid (progressive) walk On 2: quick step in place (closing, crossing, slightly open.. with or without weight transfer..) On 3: Pause / Hold
Beat 1 of the following measure gets a normal (progessive) walk again, catching up with the flow of the music. Of course, the break could also be indicated by simply pointing with the toe (on 2) and holding the position (for 3), or some other suitable type of a firulete (embellishment). No matter what, the body motion still should remain smooth here, hence giving us the possibility to dance both the flow (body) and the rhythmical pause (foot) on two different layers.