DP confusion. Do I turn left or right if not told? Please take a look at the MIA5 depatarture from KOPF:

MIA5 Page 1

MIA5 Page 2

The instructions seem in conflict. Specifically, suppose you are taking off RW 270R and want the WINCO transition.

The textual instructions are:


climb heading 273°, thence.... 
....maintain 2000 or higher altitude
and expect vectors to appropriate transition. Expect further
clearance to filed altitude 10 minutes after departure.   


OK - that
    is straightforward essentially runway heading to vectors to WINCO.

However, there is a third text segment on page 2 regarding the WINCO transition:

"From over DHP VORTAC on DHP R-322 to WINCO INT"

DHP is a LEFT turn from OPF and would take the airplane directly across the KMIA departure / arrival paths; WINCO is a right turn. Which is it? What do I do in lost comm? Why do they have "from over DHP" I would expect the instruction to be "climb heading 273° to intercept DHP R-322 to WINCO"

Also, if I load that procedure into Garmin Pilot, it just shows a path direct from OPF to DHP then to WINCO which I know is wrong.
The ROUTING is DHP 322 radial to WINCO.  So that's the course line that you'd intercept when so instructed.  There is no reason to actually start at DHP, and since you'll be flying the heading off the runway, the leg from the field to DHP in the Garmin is immaterial.  You can expect that they'll either clear you to WINCO, or (for a non-RNAV aircraft, most likely)  that they'll clear you on a heading to intercept the DHP 322 radial to WINCO (and thence as filed), so you'd cycle the active leg from the {OPF to DHP} leg, to the next leg, which is {DHP to WINCO} (which is the same as the DHP 322 radial), and then you'd intercept that active leg.

Nothing in those instructions is telling you to fly to DHP, nor should you expect that you'd get a clearance to do so.

To answer the question in the title, until you're told otherwise, you fly the initial heading in the text instructions.  You're on vectors, so don't turn until told to do so.

If you go lost comm, then AVE-F would tell you that you're on Vectors to WINCO, so get yourself there as best you can, probably by turning direct if you're RNAV equipped, or flying the radial if not.

EDIT: Note, though, that in the normal (with comm) case,the DP instruction is NOT to fly heading 273 to intercept the radial; it is to fly that heading.  That's your only CLEARANCE.  ATC will turn you to intercept on whatever heading they want you on.  Only in the case of lost comm would you turn to WINCO upon reaching the 322 radial.  In all other cases, follow ATC instructions.