A temporary moratorium that would prohibit medical marijuana dispensaries from opening in Waltham until mid-2014 is expected to be considered by the City Council’s Ordinance and Rules Committee early next month. The moratorium, popular in many Massachusetts communities since Attorney General Martha Coakley deemed them lawful last month, would give the city until next April to figure out where dispensaries should be located. The temporary ban would also give officials time to wait for Coakley’s office to release final regulations on medical marijuana, which was approved by a statewide referendum in November. They are due this spring. City Councilor Daniel Romard, who proposed the moratorium, told his colleagues Monday night that Waltham might prove desirable to dispensary owners because of its close proximity to major highways and public transportation. The City Council would retain the option of enacting zoning and other regulations governing dispensaries, and then drop the moratorium early, if it reaches a decision before the measure expires, members noted.