Getting PostGIS 1.5.3 working with Postgresql90 (Macports)

What I want to do is import some shape files, using the shp2pgsql loader. However, I need a database first, and I've read I need to make it spatially aware, which means creating it from the "template_postgis". All the docs I read indicate that template_postgis should be present after installing PostGIS. But… When I try to create a database from that template, I'm told it's missing. 

> createdb -T template_postgis demo -U postgres

createdb: database creation failed: ERROR:  template database "template_postgis" does not exist

> sudo port installed | grep postg

  postgis @1.5.3_0+postgresql90 (active)

  postgresql90 @9.0.5_0 (active)

  postgresql90-server @9.0.5_0 (active)

  postgresql_select @0.1_0 (active)

> shp2pgsql -c -D -s 4269 -i -I demo.shp | psql -d demo -U postgres

Shapefile type: Arc

Postgis type: MULTILINESTRING[2]

SET

SET

BEGIN

NOTICE:  CREATE TABLE will create implicit sequence "nrn_ab_8_0_roadseg_gid_seq" for serial column "nrn_ab_8_0_roadseg.gid"

NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "nrn_ab_8_0_roadseg_pkey" for table "nrn_ab_8_0_roadseg"

CREATE TABLE

ERROR:  function addgeometrycolumn(unknown, unknown, unknown, unknown, unknown, integer) does not exist

LINE 1: SELECT AddGeometryColumn('','nrn_ab_8_0_roadseg','the_geom',...

               ^

HINT:  No function matches the given name and argument types. You might need to add explicit type casts.

ERROR:  current transaction is aborted, commands ignored until end of transaction block