C172 INSTRUCTOR PLT CONCERNED WITH DIFFICULTY IN PATTERN ENTRY INTO SDF AND MANEUVERING AWAY FROM A DEPARTING C172 THAT APPARENTLY DID NOT HAVE THEM IN SIGHT.

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I BELIEVE OVERSATURATION OF RADIO COMS WITH BOTH ZAB; PHX APCH; AND SCOTTSDALE TWR WERE CONTRIBUTING FACTORS TO THIS NMAC. OUR FLT FROM PRC-SDL WAS VFR. WE WERE UNABLE TO OBTAIN RADAR SVCS FROM ZAB OR PHX APCH; WHICH COULD HAVE LED TO A SMOOTHER TRANSITION TO SDL TWR. WE CONTACTED SDL TWR 10 NM OUT. THE TWR WAS TOO BUSY TO RESPOND TO US. AT 8 NM OUT; WE CALLED THE TWR AGAIN. HE SIMPLY STATED SOMETHING LIKE HE WAS NOT ABLE TO GET US ON HIS RADAR. HE DID NOT ISSUE SEQUENCING INSTRUCTIONS. AT 6 NM OUT; WE CALLED AGAIN; REQUESTING LNDG. USING OUR CALL SIGN HE ADVISED US TO CALL HIM BACK IN 3 MINS. HE DID NOT TELL US TO REMAIN CLR OF CLASS D AIRSPACE. I ASKED FOR CLARIFICATION. HE DID NOT RESPOND. AT THIS TIME; WE FELT IT PRUDENT TO REMAIN CLR OF THE SDL AIRSPACE AND CIRCLE TO THE NNW. AFTER ABOUT 2 360 DEG CIRCLES; WE CONTACTED TWR AGAIN. HE TOLD US TO MAKE A 4 MI 45 DEG R ENTRY FOR RWY 21. (WE NOW WERE TO THE N OF THE ARPT.) UPON POSITIONING FOR THE 45 DEG ENTRY HDG WBOUND; AN ACFT TO THE N WAS OBSERVED. WE MANEUVERED IN A STEEP TURN TO THE R TO AVOID THIS ACFT. THE ACFT MADE NO MANEUVERS TO AVOID US; AND SHORTLY AFTER CONTACTED SDL TWR (APPROX 3-4 MI OUT). I BELIEVE THE SDL TWR IN ADDITION TO THE OTHER ACFT CAUSED THIS SIT TO OCCUR BY NOT GIVING US ENTRY INSTRUCTIONS WHEN ORIGINALLY REQUESTED; THEREBY ONLY INCREASING FREQ CONGESTION AND POSITIONING US IN A DANGEROUS LOCATION WHERE OTHER ARRIVING ACFT WOULD BE TRANSITIONING.